Originally Posted by foofopps
No shit, that is true in theory. However you are still a moran for thinking that principle can be applied to the 128i PE. This is not a mufflerless system like the berk race which I happen to have on my 135i.
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.