This is very much a taste thing...Some exhausts make the M sound is raspy, others lose the essence of the car. Plenty of diff systems on Youtube...IK - Gruppe M - Overpriced and imo the design is no where near as good as some of there other ones. (DC5/E46/355 etc) Thorney are making a CSL replica which is worth a look. Also Birds/carbon goeke are makin some tidy stuff..>All at a price tho.