Originally Posted by CombatNinja
335is is close to the Performance Exhaust. Close enough that I wouldn't bother making the swap. One thing to consider is that the 335is is N54-powered while your 2011 335 was N55. Those always sound a bit different even with identical exhaust setups. Not to start a flame war but I think the N55s sound a bit better all things being equal.
I have the PE on my N55 and I heard a stock 335is and they do not sound similar to me at all. But sound could be subjective to individual tastes.