I would actually suggest running with the Eisenmann Exhaust for you car which comes in optional 2x90mm tips, 2x102mm tips, and the great 4x76mm tips as pictured below:
Mote, thanks for letting me use the video 
You can find his thread here:
Eisenmann Race Exhaust - e92 335i
http://www.e90post.com/forums/showthread.php?t=234600
Let me know if you have any questions