Has anyone yet considered the fact that the turbocharger acts as somewhat of a silencer and that's one reason why the exhaust doesn't immediately change tone when the muffler is changed out? My wife's 2011 128i convertible has the BMW Performance Exhaust and is 3 times as aggressive at startup and idle as my 2013 335i with the MPE and MPPK. On a cold start, when the wastegate is wide open, it's comparable, but once the wastegate closes, it gets much quieter. When you get on it and the engine is under load, the MPE gets louder, same as when I had Dinan exhaust on my previous E92 with the N54 engine.
All that said, the MPE does sound much better than the stock unit, and does require some "break-in" miles, but it's not going to make any Lamborghinis pee their pants...
