In my experience (2008 E90 M3 and 2012 E92 M3, both with generic mufflers and custom tips), the Magnaflow mufflers drone will tone down considerably by itself after some 3000 miles or so.
Like you, at the beginning (twice
) I thought that I made a mistake because the drone is a mofo between 2500-3100rpm. But after the E90 M3 experience I had to get them again in my E92 M3. For the price ($350-$450 installed) they cannot be beat in sound, IMO.
-2015 F30 320i, Imperial/Oyster, 8AT, ED
-2012 E92 M3 Jerez Black/Rust Brown, M-DCT, ED: Gone
-2008 E90 M3 Melbourne Red/Bamboo, 6MT: Gone
-2007 MK5 GTI United Grey/Grey, DSG: Gone
-2004 E46 M3 Carbon Black/Cinnamon, 6MT: Gone