http://www.e90post.com/forums/showthread.php?t=694465
http://www.e90post.com/forums/showthread.php?t=661826
http://www.e90post.com/forums/showthread.php?t=608932
This oughta get you started, have fun with exhaust set ups, I have 3 at home. Dealers know about my car and they don't give me problems and the car still runs like a champ.