Originally Posted by Kim Schwartz
I had an aftermarket performance exhaust for a Miata and on the track it was great but on the street I noticed the lack of low RPM torque much more than I noticed the increase in high end HP. That said I have the BMW intake and exhaust. My wife also has a 128i but with stock intake and exhaust and I percieve no loss in power in my car. If anything the throttle response is better with no flat spots. I've never driven them side by side at high rpm's to comment on if there is a noticable gain there but I am delighted with my car.
My active autowerke exhaust on my 128 had this effect to a degree. While i didn't necessarily notice less torque down low, I instantly noticed it rev's way faster to redline then it did with the stock or PE exhaust. It's especially noticeable when you do a WOT run in 3rd, as soon as you get to about 4-4.5k rpm it starts pulling harder and faster then before it. Though i do get what most people would consider an annoying amount of drone, I can live with it because i enjoy having loud cars. Especially coming from my old 2.8 turbo diesel jeep with a straight piped exhaust