3.0i Header Options
 

I was thinking of installing a set of exhaust headers for a little more sound/performance, but after searching, I'm really only seeing 2 options out there:

1) cheap ebay headers for about $100
2) something like supersprint for $1500+

In looking at realoem, it appears that the E53 and E39 use the same exhaust manifolds for the M54-equipped cars. However, all the ebay listings that list fitment for the E39 show the same part for the E46, which I understand will mate to the head but are too short and will need custom work to attach to the E53 stock exhaust.

Is there a decent quality bolt-on solution in between? I'm willing to spend more (not $1500), but even the few see for $5-600 appear to be the same cheap ebay headers for the E46 just at a higher price.

Also interested in this...

Honestly, I don't know that there is a reason to spend more than $150 for the headers and then about that for new, good quality cats. I arrived at that conclusion by reading a ton of e46fanatics.

There is not a ton of power left on the table on the exhaust side on these motors where X5s can use it - the M54 and S54 motors were designed to make torque up higher in the RPM band than A)is useable by a 5500lb truck, or B) it turns out is feasible for the M54 because the harmonics over 6k rpm are bad and the oil pump nut might spin off, so you don't want to be up there anyway.

Go look at dyno charts of M54 to confirm that.

The major point I see on the X5 exhaust manifold is that the bends right off the head are tight and the cat is mounted way up high to get it to light off faster so it could make the higher tier of emissions (PLEV...some stupid acronym).

So I don't know that other than having better bends and having hi-flo cats there is much to do on an M54. I have a set of ebay headers I am about 25% of the way through getting on. There are about 4 different kinds of ebay headers that fit, but they are all more or less the same 2 designs. And then there are the 1500 ones.

EDIT: You have a Z3 - I actually looked at using factory Z3 manifolds, which are more like a header, but IIRC there was some emission thing they had/didn't have that I did not want to bother with. The high level Z3 and 330 OEM steel header type manifolds look pretty good. Could be an improvement over X5 OEM.

Yeah, I see what you're saying. I'm not looking to get every last ounce of power. What I'm trying to avoid is having a nice-looking set of stainless headers connected to some crappy looking exhaust shop adapters then on to the factory exhaust. That, and just the trouble of getting it done - i.e. finding a shop that can a) do nice TIG welds in stainless and b) will work on a car without cats.

If I go that route, I'll probably spend a few more bucks and go for these Schmiedmann's vs. the bay headers:

https://www.schmiedmann.com/en/bmw-E...ct=SCM5254MANI

I have a set of BimmerBrakes headers on my E46 325Ci (M54B25).

These headers will also fit the M54B30 in the E39 and I am guessing the E53 as well...

I dont know if they are still making them as I bought these 5 years ago, but they have been great in terms of sound and the butt dyno :)

Going to source a new set for my E53 3.0i soon...

*EDIT*
They actually have two versions now

This is the one I have...
BimmerBrakes SS M54B25/M54B30 V1 Performance Headers - EuroPartsOnline

Version 2
BimmerBrakes GEN3 M54B25/M54B30 Performance Headers - EuroPartsOnline

Version 2 looks like it might have equal length ports vs the V1... is that worth $75 more though??

We went with MagnaFlows and we could not be happier. I swear, we gained 25-30HP, the truck pulls like crazy. I though it was all in my head until my kid drove it for a couple of days and said the same thing. They are integrated manifolds & cats, and loving the the SES light is gone and we passed our emissions test finally! Here's the part numbers for our 2002 3.0 E53:

Magnaflow 49772 | BMW 525I/530I/X5 | 2.5L/3L | Front | Catalytic Converter-Direct Fit | OEM Grade EPA 49772 1
Magnaflow 49773 | BMW 525I/530I/X5 | 2.5L/3L | Rear | Catalytic Converter-Direct Fit | OEM Grade EPA 49773 1

Direct fitment and even come with front & rear gaskets, rear bolts, etc. We paid $1,087 for both shipped with an online coupon. Hope this helps!

Check out e46 fanatics. There doesn't seem to be much a benefit beyond the eBay headers.

Bringing this back up. I just installed 4.6is mufflers and got just a little more sound, still too quiet, though, IMO.

After looking at the manifold to center section transition, I was able to have an educated conversation with several ebay sellers about their fitment. Conclusion is that NONE of the China/Taiwan headers will mate up to stock exhaust on the E53/E39 M54 engine even though several claimed they did. Neither does bimmerbrakes or racing dynamics (to give them credit, neither of those claim to fit but some of their resellers claim E53/E39 bolt-up fitment).

However, after talking with the sellers of "russian ebay headers" aka bmwdoctor.ru, I have some confidence they'll bolt-up to our stock exhaust. They swear it does and sent pictures that at least show the correct flange clocking.

So, with a one-day only 20% off ebay coupon ($450 delivered), I'm giving these a shot:

Russian Ebay Headers

Based on their instagram page, I suspect they're buying them from somewhere in asia and correcting the output side to fit various other models correctly. Over on an E90 forum, someone posted pictures and the comments were they look much better than the standard China-headers but aren't up to par with supersprint.

Do you need to use a cat simulator to pass emissions?


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There are a few options to pass emissions without integrating cats into the exhaust:

1) Use the euro tune that will suppress the check engine light, but this will only work if your state doesn't require all OBDII monitors to be in a "ready" state.

2) Some have had success using spark plug anti-foulers/o2 sensor extensions that put the after-cat o2 sensors out of the direct exhaust stream keeping their readings within tolerance.

3) Use real o2 simulators for the after-cat o2 sensors to mimic the correct values the ecm is expecting

4) I don't know if anyone has done this successfully yet, but adjust the parameters for the after-cat secondary o2 sensors so that they'll accept any value without impacting monitor readiness.

For me, this is one of those "cross that bridge when we get there" situations. I've done a lot of tuning on GM cars to this effect and am hoping the same can be done here. If all else fails, it's re-install the factory manifolds every other year - tho yuk.

I recently read the best first step for improved performance is new headers that's why I'm curious


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Modern high-flow cats are not going to be a drag on performance. Ground-lying, smog-forming and carcinogenic emissions and are a drag on society.

There is not a lot of power left on the table in an M54 exhaust in factory form, and for proof just look at ZHP manifolds. They are not big and they are not complicated. What they don't have is a cat mounted right up on the head to light it off faster to make PZEV emission standards like E53. But that doesn't mean get rid of the cat. It's not your enemy. Compromise of design is.

The russians are here!
 

I received the russian ebay headers (bmwdoctor.ru) and have to say they look pretty damn good. The welds (TIG) and transitions look good, and they're 14 gauge tubing.

I don't know about the fit yet as I have to run through emissions before installation, but the flanges appear to be correct for the E53. They're definitely not the generic E46 headers you see everywhere else.

Sorry I don't know why the forum is resizing these pictures so HUGE!!!

http://www.guldstrand.com/images/20180320_131833.jpg

http://www.guldstrand.com/images/20180320_131839.jpg

http://www.guldstrand.com/images/20180320_131824.jpg

http://www.guldstrand.com/images/20180320_131855.jpg

http://www.guldstrand.com/images/20180320_131957.jpg

Sub'd

Looking forward to seeing them installed. Good luck

Let me know if you can't get the check engine light out

I just ran through emissions testing so hopefully I can carve out a day in the next week or two to get these on.

As far as the CEL goes, I'm going to buy a spare ECM and tune it out. I found a wealth of information on the MS43 wiki:

MS43Wiki

I'm VERY familiar with tunerpro, etc., from burning chips for my vettes. Tuning the MS43 will be the same except the calibration is loaded via flash instead of a PROM burner. This will be fun...

Awesome, can't wait to see how fitment will be! Thanks for doing this!

Also, my plan was to wait until Black Friday as SuperSprint runs a 50% off on Turner Motorsport, I was planning on getting both the exhaust and headers.

It usually takes 3-4 months to ship to you, but worth it in the end.

FYI - ECStuning currently has the E53/E39 supersprint headers on sale for $730 (56% off)! Looks like the cat back isn't on sale, though. That price seems a lot more reasonable given the now low resale values of our X's.

I did a test fit yesterday, and they're looking pretty good. They definitely bolt right up and don't interfere with anything. The flanges are clocked correctly, but might be off a degree or two in how they're angled. In the pictures everything is loose fitted except the header-to-mid-pipe connection. It may that all hangers downstream aren't snug or that the flanges are off a degree or two, but I think they will be OK when tightened down and heat-cycled.

The only other problem is the lower o2 sensor on the rear header will hit the floor pan. If the bung were clocked just a few degrees more, there'd be no problem. I can probably get the sensor in as is, but it will rub.

Overall, this job is a complete painintheass, but I'm very happy with the quality/fit of the headers, especially compared to the nightmare stories I've read about others having to re-weld flanges, grind motor mounts, etc. They even got the clearance for the sway bar right.

Question - do I even bother running rear o2 sensors? Is there any advantage with an EU2 tune or otherwise? The alternative would be to get a 45 deg angled spacer/adapter, and then that sensor will fit just fine. I'm leaning toward just buying 2 new ones for the front and skipping the rears.

Install finished
 

I finished up the install, and everything mated up just fine - no leaks! There was no way I could get a torque wrench on most of the header-to-head flange bolts, but I did add the missing studs and snugged all of them up the best I could.

I decided to delete the rear o2 sensors and use the supplied bung plugs. And, even though I was super-careful not to swap the front o2 sensor wires, somehow I did. The car would run rough and hunt for idle after warm-up. It's easy to tell in INPA if you swapped the wires, just run the lambda sensor test, and you'll see the values move on the wrong bank.

Overall, even though it's a tough install job, I couldn't be more pleased with the quality and fitment of the russian ebay headers - they bolted right up without trouble.

The CEL came on after about 5 miles of driving. I just got a spare ECM to mess with tuning. More on that later...

Sound - not much at idle. It sounds maybe slightly quieter than my old Z3 3.0 but with two tailpipes. At cruise, you can barely hear the exhaust from inside the car. It is a bit louder at higher RPM's during WOT.

Performance - I feel no difference in torque or at lower RPM's. From 3.5k on up, it feels peppier, and I'd say the +15hp or so dyno tests others have reported on e46fanatics seem to be spot-on.

Next up - ESS twin-screw supercharger?

Thanks for this info! Solid work.

I need to replace my cats and I am leaning more towards not doing headers because of the smell etc. I hated it on my e46 at stop lights

I am more interested in hearing about the removal of your stock cats. Any special process?
Did your studs come out with the nut as well? Clearance issues?

I highly recommend doing headers even if you integrate cats as the stock manifold/cat combo is VERY restrictive. Maybe some of the aftermarket manifolds like pacesetter or magnaflow are better. I'm easily getting 10% better MPG's now and quite a bit more power in the mid to upper RPMS.

If I were to integrate cats, I'd use the same headers I got as they fit well and seem very well built. I'd cut the center resonator out and merge the pair of pipes into something like a single 3" cat and then Y it back out to the pair of pipes that goes on to attach to the rear mufflers. It's a straight shot, and you could probably even do it without welding if you don't mind a few extra clamps down there.

But, to answer your question on removing the manifolds, it's not that hard but is tedious. The sway bar and reinforcement plate need to be removed. My car doesn't appear to have ever seen salt, and all nuts/bolts were pretty clean so YMMV.

I don't know if it's required, but I did remove all O2 sensors first. Getting at all the nuts on the head was the tedious part. Some came off in a minute or two while others took 1/2 hour each. Have lots of extensions, wobble extensions, universals, short and deep sockets, etc., handy. They're not that tight and 1/4 ratchet worked for me on most of them even if I had to break it with a box end wrench. I'd say 1/4 to 1/3 of the studs came out with the nut. It's no big deal once the stud's out, just spin two regular nuts (M7) on and back off the bronze lock nut. Then do the same to spin the stud back into the head. I did about a third of them from above and the rest from below. The front manifold will come out first and then the rear. Both have to go out the bottom.

That's all I can think of - good luck!

well that's great information to know. I was kind of hoping that you would tell me it's not worth it but now you have me leaning towards getting headers again. Can you elaborate a little bit on the smell from the car. do you have to always keep the windows rolled up and would it be to the point where my neighbors would be complaining as my car is on idle?

Did you also do everything by yourself or did you get help?

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Also forgot to ask what method you went with to get rid of the check engine light. Does this mean your car will run lean because it doesn't have O2 sensors at the moment? Especially at the rear I see you have them plugged.

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I imagine the smell would be the same as your old e46. In the e53, you're a little farther away, but if the air is stagnant, I can see it wafting up front or to the car behind you with the windows down. Nobody has ever mentioned to me that my car stinks, but it's rarely stagnant around here.

It's definitely a one-person job, not really room for two.

Regarding the CEL, if you don't have emissions, it's very easy - just flash it with the BMW EU2 calibration (can be done using all BMW tools - basically makes the car euro spec). If you do, it's a little more involved as you have to do a custom tune that turns off the post-cat sensors so it doesn't throw a code for those. In either case, the front sensors are still used and the mixture is correct. The rears are only there to monitor cat efficiency and make very minor fuel trim adjustments if the front sensors are a little lazy.

I am definitely doing this the hard way. I got headers that look like they are the same as those pictures until the flange...I don't have any flanges. I am adding cats there, so I chopped down the headers and MIGed on some vbands. Tonight I hope to weld vbands and 02 bungs onto my new 400 cell cats, and then I can put the front section back on and see if it runs. I haven't run it in a long time.

I have been having a deuce of a time getting the new studs in the head with the two nut method. I get them in, but then when you expect to feel the stud bottom in the hole, the second nut will start turning as well so you never really feel them hit--even though they are probably threaded all the way.

The cat on my daily driver is hitting the end of life. It smells awful, and it's a tin can VW with a 2.5. I can't imagine an m54 with no cat. Probably reeks, and should come with a Prop65 warning.

Be careful where you put those cats! Make sure there is ample heat shielding above where you integrate your cats (heat rises). Would hate to see you engulf your cabin in smoke from smoldering carpet backing. The flange area looks risky to me.

Re the studs, don't crank them in too tight or you risk cracking the head. Just crank them in until they don't move anymore under modest pressure. Visually gauge the length of engagement and don't force anything.

If your VW is smelling awful with a failing cat, it's running rich, and that's what's probably doing in the cat (cats don't have a service life on a properly calibrated engine). Remember, all a cat does is accelerate a naturally-occurring reaction (oxidation). That smell you refer to is unburned fuel going out the tailpipe. Complete, un-catalyzed combustion hardly smells.

Yes, I'll look at the fuel trims again, but mileage has been within expectations. The plugs are old but I can pull those and see how they look. No other codes on the VW besides cat efficiency. Could be a leaky injector or a vacuum leak, I suppose.

I am going to stick extra shielding on the cats between the body and the floorboard. I'll have enough space to add a very short bracket and a bunch of aluminum plate between them and everything else.

The flange area is tight left and right but fine up and down, as far as fitting these small-bodied cats in goes. I have to get them in staggered fore and aft, as they are slightly too wide right next to each other.

Eventually I will put a new resonator in if this all works, but for now its going to be more chop and weld at those flanges on the midpipe. I saved the OEM ones I chopped off the manifolds, just in case I can use them again, but I think my header-cat assemblies will be too long.

Wonder with the angled adapter of you used them for the post 02 sensors if the light would even come on!!?


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Did any of you chase the manifold stud holes? I know they are 7mm and most go in no problem, but the ones that never had a stud before are a bit belligerent.

Not understanding what you're referring to when you say the ones none had a stud in? Should they all have studs in them when you're removing them?

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Certainly worth a shot - it's cheap and easy and others have had success with this method. I would guess the longer the adapter the better, and I've also seen some with restrictors (smaller hole into the exhaust pipe).

No, the factory manifolds do not use all 24 stud holes.

The stock manifolds only have 16 studs/nuts attaching them while headers have holes for all 24 (4 per cylinder). There shouldn't be any 'junk' in the unused holes as they would have been covered up by the original manifold/gasket. Maybe blow a little shop air in them just in case?

So that would make sense on why I have to buy new studs

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This should illustrate m52/m54 eBay header install.

https://youtu.be/Cc3DxEE-0pc

Everything eventually bolt up? I am a few weeks away from doing this. I am going to stick with stock cats as I don't want to deal with the mods around headers again and the smell.

When you are bolting the studs back in with the 2 nut combo and backing it back off, do you actually have the room to work with the wrench doing this? Curious if you had more tips around this since you probably completed it.

Everything bolted up perfectly, and I'm enjoying about 10% better mpg and what feels about the same increase in power.

It is tight in there, but I found room to use the 2 wrench/nut combo when screwing the studs back in. I used a combination wrench and a 1/4 ratchet with shallow and deep sockets depending on where I was working. Also, some were easier to get at from the top while others were easier to reach from underneath.

One other key is to buy two regular (non-locking) M7 nuts to screw the studs in. That way, when the stud is in, you can back one nut off slightly and unscrew both with your fingers.

I got mine bolted to the head, but I'm still vband flanging my new cats to the end of my headers. If I can't figure out a good way to get from the cats to the stock x pipe, I might have to cut that out as well and put in a borla.

I figured out something interesting...no E53 exhaust manifold gasket has 12 holes per gasket in it. That means if you want to put OEM gaskets on headers for the sleeper look, you would have to drill press the gaskets carefully. Also, the gaskets that come with ebay headers look suspect, so you can use E36 328i gaskets, which are MLS gaskets with all 24 holes. No heat shields though. If you wanted to (I thought about this but did not have the patience) you could chop down the OEM E53 gaskets and mount them outside the headers.

Getting the nuts on with the heat shields on is terrible, though, if anyone is wondering.

Do you have data to back that up? Nothing about intake and exhaust mods should ever change MPG in gasoline engines. Power yes, mpg no. That's not absolutely always the case, but it's so rare that I'm always skeptical unless there are fuel logs showing it to be the case. (Not dash readings)

Less restriction will give you less power loss means more power to the ground vs heat loss. This will mean better mpg but 10% not likely at all. If that was possible all the X5 would have high mpg headers.

On gasoline engines, you restrict them using the throttle. If you open up the exhaust, the engine will pump more air/fuel mixture at any given throttle position. But when cruising (ie not at WOT) you will just compensate by opening the throttle less than before. The throttle is called a restrictor plate for this reason. There's generally no efficiency gain to intake/exhaust mods because of this. Power gains, though, are obvious.



Diesel engines, that is not the case.

The efficiency gains will therefore only really present at wot. The gain will therefore go more toward faster 0-60 than farther range. Power is energy/time. If you don't use the energy quickly (higher power) it will mean more time to consume or higher mpg

Power is energy per unit time. Efficiency is energy out divided by energy in. Higher power does not mean higher efficiency. It's true that you might see higher efficiency at WOT, but nobody drives at WOT all the time, so it won't make a difference.


Meanwhile the rest of Xoutpost thinks "nobody drives at WOT all the time? Challenge accepted..."

I agree. I run hard almost all the time and my daily routine usually involves hitting 200kph (until I get hit by a flashy cam)[emoji38]

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The trip computer is VERY accurate. Afterall, your ecu knows EXACTLY how much fuel it is injecting into the engine at any given time and how many miles since reset. By the trip computer, I could never do better than just shy of 21 mpg on highway trips, and now I'm getting just shy of 24 mpg on the same routes.

Intake and exhaust mods can very well change the efficiency. Ever hear of pumping losses? Think maintaining 600 deg temperatures in a catalytic converter is done without expending any energy? You often hear that an inefficient exhaust system only costs 2 or 3 hp or such and such, but when the vehicle only requires 20 to 30 hp to maintain it's speed on level ground, there's your 10%.

Like I said above, pumping losses are negated by the fact that gasoline engines are restricted. You take them away from the exhaust and then add them back in with the throttle (which is literally a "variable pumping losses" valve). That is just how gasoline engines work. "You often hear" a lot of things repeated on the internet. And converters are heated by the capitalization of leftover fuel and oxygen (literally burning the leftover fuel). They are not heated by friction or pumping losses.



Trip computers are flawed measuring devices when new, and more so when old. We all have met the C5 Corvette owner who thinks their cars get 30mpg everywhere they go (that's an extreme case, but the C5 owner could argue the same thing you are arguing). The only way to prove it is fuel logs. Even modern cars are inaccurate due to many different factors, and OEMs even program inaccuracies into them. I can prove this with the many years of fuel logs I have for my own cars. I have zero problem believing everything you say if you back it up with fillup logs.



Great work on the headers, and thanks for posting all your work on the forum for all to benefit from.

My wife and my near identical cars get wildly different mpg. She gets 23/24 I get 20/21 highway. Head on nail for energy is energy. If it's expended heating something that energy didn't push the car forward.


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The gas that heats the catalytic converter would just be dumped out the tailpipe into the atmosphere. That's what cats do. They clean up the unburned gasoline in the exhaust, as well as other reactions. There's no less gasoline going into the exhaust by removing the cats.



The reason they heat up is because it's literally equivalent to a flameless burning of that gas with air. The energy in the unburned gas has to go somewhere. Removing the cat doesnt make the engine put any less fuel in. It just dumps it out into the atmosphere in a form that's more polluting.

I disagree. The trip computer is not accurate in my experience. I log all of my fuel ups and track my mileage. My OBD consistently over reports mileage by .4 miles per gallon. The ECU does know exactly how much fuel it's putting in the engine, but I don't think that is how the OBD calculates MPG. In fact, my scanner has a function that allows you to adjust the reporting accuracy of the OBD. Unfortunately, it only works in liters not gallons. I haven't been able to figure out how to make the adjustment correctly. The adjustments I tried only made it worse, so I went back to "neutral".

Very true that the mpg is not necessarily that accurate but the change should be reasonably accurate. That said, I've seen big changes in mpg after changing some component like the O2 sensors but after 100 miles back to normal.


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I hoped I would see a change after changing my O2 sensors that had over 200k miles on them. Nothing. I even went in and cleared all adaptations on the truck. Still no change. Oh well.

Exactly. I would even argue that the computer doesn't know how much fuel its putting it. It's just modulating an injector pulse width to hit an O2 sensor value that it deems to be correct. All of the sensors and devices involved drift over time: the airflow meter, injector flow rates, O2 sensor, and even the wheel speed sensor due to changes in the tire diameter. The computer isnt concerned with making sure your MPG meter is right, its concerned first with maintaining emissions, then AFRs. That's why logs are the only truly accurate way of measuring changes in MPG.



You're also exactly right andrewwynn, that the computer learns how to react to changes we make when we modify or maintain the engine, and sometimes it takes a little time.

All I can say is that the replacement of the stock manifolds, which look like a terrible design to me for performance considerations (outside cylinder charges run directly into each other and then make a sharp 90-deg turn downward), netted me a not insignificant increase in power in the mid to upper RPM range (SOTP measurement) and a ~10% increase in highway mpg as measured by the trip computer.

I've always found my trip computers to be pretty accurate, and I don't buy that it will all of a sudden drift off like that.

BTW - I had a C4 corvette with the 6 speed manual and easily got 28 mpg hwy and could top 30 if I kept the speeds 60 or below. This was measured with fuel/mile log. The L98 TPI motor is tuned for low-end torque and turns about 1600 rpm at 60 mph with it's 3.33 rear gear and 0.5:1 OD ratio.

Do some full tank mpg mpg measurements. It would be awesome to get an actual measured increase


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I'll do that next time I take a longer drive absent heavy traffic.

Yes. Quoted for posterity.

UPDATE: Decided to stay with Catlytic Converters. Mine had a massive crack in them which would explain the "puff puff" noise. First set i ordered on ebay. Learned my lesson and I cannot be mad at it. Nothing Lines up.. Returning and another member mentioned he used these (Links below) with is a performance brand that MangaFlow bought out in 2017. He said they bolted right up. So with the free time waiting for shipping, i did my Valve Cover Gasket, and replaced all the studs.

For anyone doing this on the 3.0 X5, you DO NOT have to remove the stabilizer bar, just remove the bushing and gently adjust it out of the way.

BOSAL is the brand..
Front
Rear

I thought I was going to light the fires again last weekend, but when I chopped off the OEM flanges into the resonator, I found one to be 1 7/8 OD and the other to be much closer to 2". So my 1 7/8" ID adapter from my 2" cat fit over one pipe, but was useless on the other.


Is that a design feature, or a manufacturing defect?

I'd be surprised if it was a manufacturing defect. I believe the 4.6is had different pipe diameters L to R(by 5mm IIRC), and they are both metric - something to keep in mind. Maybe the 3.0 was the same for packaging reasons.

My exhaust manifold gaskets were kind of flimsy and when I pulled on them they separated.
After some research I found this to be a common problem, with people usually experiencing rattling.
I unbolted almost all the top bolts and I'm planning on changing the manifold gasket.
However with the manifold off, I was thinking of maybe installing headers and found this thread.
The russian headers come to around $800 CAD which doesn't seem sane.
Are there any cheap ebay headers that would fit properly?
As I don't have my engine out, I can't drill and tap extra holes and I want to avoid this situation with exhaust leak
https://youtu.be/Cc3DxEE-0pc

From 6 pages of this thread looks like the only person who actually installed the headers is e39_touring
And another person paid around $1000 for headers and catalytic converter.
Let's see if anyone else was able to successfully replace headers for cheap with a proper fit??

I haven't been on in a while, but if you're still considering headers, I'll chime in. Yes, there are still ~$100 headers on ebay. Don't worry about the head side. Mine had all the holes drilled & tapped from the factory. Just buy some extra studs/nuts, and you'll be good to go there with no leaks (I recommend factory-style gaskets that incorporate a heat shield). I believe they omitted those few studs/nuts on the stock manifolds because they'd be near impossible to get a wrench on with the engine in the car.

If you see headers that say they'll fit E46 and E39 (as most do), they're really E46 headers. They'll bolt up to the head just fine, but you will need to do custom work to connect to your exhaust system. At a minimum, the flanges will be clocked wrong, but the length may be a little different, too, causing you to add pipe to fill the gap.

The only ones I've found to work directly on the X5 are true Supersprint headers or the Russian headers I bought. The Supersprint are pricey, but I have seen them on sale for ~$700US (still a lot when you convert to CAD).

You pay your money and take your choice. I chose direct fit without having to get the header-to-exhaust fabbed up, which wouldn't have looked as clean and wouldn't have saved a whole lot of $ in the end. Still enjoying my setup though I don't really drive much these days!

Thanks for sharing your experience.
In the end I decided to stay stock.
I'm just sanding off some rust to make it look good and then gonna paint it.
I'm thinking of using some additional rivets to attach the gasket and the heatshield together so that they don't come apart.

Nothing wrong with stock for normal use - it's certainly the best-cost option!

Re: the heatshield, I'd recommend using the factory-style exhaust manifold gaskets (Reinz) as the heat shield is sort of integrated into the gasket. I'm not sure how you could securely attach the heat shield to those small header-like gaskets without getting leaks. Look at pictures online, and you'll see what I mean. The factory-style gaskets have a ring around the exhaust port that sandwiches the heat shield and the gasket material in a way that I don't think you could duplicate with the separate pieces.

I think I wasn't clear enough and you misunderstood me.
The gasket and heatshield are one piece, but held together with only 2 rivets. See pictures attached. The problem is, with time these rivets rust out/gets destroyed by heat etc. I don't know what exactly happens, but the heatshield portion becomes loose and can make noise.
I was able to just pull on the heatshield and remove them by hand. That's when I learned that they were part of the gaskets and removed the manifold to replace the gasket/heatshield.
As you see on the picture, there are only 2 rivets.
I was thinking of adding extra rivets to make sure the gasket and heatshield are held together better and don't separate.
https://i.ibb.co/m0LMFLg/20200425-150219.jpg https://i.ibb.co/swXPf6m/20200425-150154.jpg https://i.ibb.co/yWc5bkq/20200412-205251.jpg