Well any additional (HP)/pressure will cause wear & tear - just like on car that you would use for towing. If you ever used your X5 to tow stuff - after 2-3 years there would be greater wear/tear then just driving car alone.. but around 120 HP is still respectable #'s - if we were taking about 250HP+ that would def do something to the tranny/mounts/etc - but 120HP is still in respectable limits I would say.. And it also depends how you treated your car since start.. if you floor it every light to light since day you bought it - i would understand the trans to be used heavily - and adding 120HP to a few years old tranny is putting more strain on a old horse- but if your just purr like a kitten around town in your X5 that you dont beat up on every light - trans still is good & strong & I dont think extra 120HP would destroy it - just put more wear & tear on most usable parts- that you would normally put on car anyways depending on your life-style & what you use car for.

I searched for several months for an E53 turbo or supercharger kit that I could DIY. I checked on custom turbo kits from local BMW indy and STS. Both prices were custom single turbo systems that would take 3 weeks to complete. STS had to have the X at their home base. Both prices were between $6,500 and $7,000. Dinan, just for the system is about $10,000 except when the have the early spring sale. I priced out a custom system that was to be between $8,500 and $9,000 installed. The custom systems were only estimates. Dinan posts the number of hours for install. Dinan must be installed by an approved installer so it is not a DIY.

I ended up going with a 150 shot of nitrous with several safety measures. Love it. Transmission is original.

Post redacted: I didn't read OP's original post properly.

My apologies, OP.

Correction: If you want to do FI on a V8 E53, the best thing to do would be to buy an off-the-shelf unit from ESS or Dinan. Doing a turbo on an N62 would be a nightmare (and that's not even considering the tuning you're undoubtedly going to have to have custom done).

Why do you have to be so cruel, OP was just asking. I didn't see a kit for a any 8 cylinder
X5 from TechniqueTuning. Are you saying he will build a custom kit for a 4.4, 4.6, 4.8 for $6,900. I would be interested if it is a DIY.

Dinan is the only way to go with a supercharger , and it is not cheap, $10k ...........and the You are running at 450HP..................but also You have to install the throttle body,and exhaust................

Dinan offers software, high flow intake and throttle body. I don't see the high flow intake on website, maybe the intake on the 4.8 is high flow, is not clear. If you couple that with a high flow exhaust you will have a significant gain. There are others that offer software also.

The same transmission is used over here in oz on a couple of factory high performance turbo cars. They can withstand a fair amount of abuse and horsepower.

My post wasn't intended to be cruel. It was more of a rhetorical statement intended to prick, if anyone, the vendor selling the kit that the OP refers to. In other words, I find it rather obnoxious that any vendor thinks they can get away selling any turbo kit for any car for $1,600. My post was not directed at the OP in the least bit.

Also, I'm not sure why I glossed over the fact that the OP mentioned he had a 4.8is (even his board name has "4.8is" in it). I probably got caught up on the link because the kit it advertises is for a 3.0i ... at which point I made the NickG association ... and then got rather annoyed, sending my reasoning out the door. My mistake.

And, no, Nick doesn't do any V8 stuff. I know he does do custom stuff, but the only custom work I've seen has been on the I6 stuff (M52, S50/2, & M54)

That said, previous post has been redacted and corrected due to irrelevancy.