Another vote for the OEM mod. The original thread is still running if you do a quick search. Sounds as good or better than anything you can get shy of 3 grand, for about 300 bucks.
2011.5 LeMans Blue e92 DCT, ZCP, European Delivery. Edition Grilles, Reflector delete, Rear Fogs Enabled, Borla/Encore Innovation Exhaust, LUX Angel Eyes, 255x285's, Dinan 3.45 Rear, BPM Stage II. "Last of the V-8 Interceptors, a real piece of history..."