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

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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?