I had my stock exhaust on from 3 miles to 62,000 miles. It didn't really get any louder or quieter in my opinion. If you want it to be a little louder, just do the OEM exhaust mod. Great sound improvement in my opinion.
Former e92 M3 owner
Relapsed M3Post addict
Hopefully getting back into another ///M soon (or P-Car)....P-car as in Prius.