I must say I am content. The sound is nothing of that of the e36 (annoying,loud), instead it gives it an M3ness that is nice and smooth. Between 1500 & 2200 rpms there is a nice hum which is pleasant to the ear. As far as performance, well we all know that you really don't feel anything on such a mod...I would say if anything I feel a bit of a pep when accelerating. The installation was simple, perfect fit..even my mechanic was impressed. I think once I have installed a 9" cone filter that I will be happy with the sound of the 6. (of course, it will never sound like a car on the european market)
anyway, just wanted to let any interested parties know.
ibBERTO & my thoughts