Revisiting an old thread I started to some things up:
Went with the Mperf exhaust and am very happy
The Mperf exhaust brings something special to the car. You look at design of tips alone, they look clean and unadulterated. Sound is amazing. Very silky "exotic" tone as others have stated. The more you drive the more you realize where it comes alive and sings. Never obnoxious, or droning, simply intoxicating. Not taking away from the OEM exhaust mod, but this exhaust IMO is well worth the cost.
If you are looking to refine the sound of your M to pure bliss, look no further.