Guys, don't worry the engine note being too muted.
I used to frequent the BMW M Power forum.
Several people with M135 or M140's - would remove the stock exhaust and "upgrade".....this engine is seriously fruity with the right kit on it!
Moreover, there are several German tuning companies - that can fit auto opening exhaust, that are serious loud but then can be closed, so you can get the best of both worlds?
Mark