The problem with any aftermarket exhaust on the M5 is cold start. There is so much pressure from
the exhaust that it could probably shake a small building if placed right. If your neighborhood is that
strict about noise and your going to be starting the vehicle at night or early morning then I would suggest having
it in a garage or at least out of sight. It's loud! However, once the revs settle down it gets very quiet at idle.
Cruising in 1st gear yields an amazing, but loud noise. Although, being quiet in the neighborhood will be no problem cruising at low rpm in 2nd gear. The drone? Compared to stock there isn't much at all. There might be a little around 3000rpm under
load on the highway, but it's faint. Power? There are many dyno graphs floating around on the forums that show 20whp+.
To sum it up I think this is the perfect exhaust!
For a 20% quieter sound there is the limited edition GTC mufflers.
http://www.m5board.com/vbulletin/m5...-rpi-limited-edition-gtc-muffler-sec-3-a.html