Most modern MB engines do not suffer from any sort of strangulation. Opening up the intake side would also mean increasing the flow right through the system (head and exhaust).
For some reason that I do not know, the MAS is picky about the air filter being in top shape and OEM. Could be that micro particles damage the film-wire? OBDII MAS's are just plain unrelaible as it is, and I would take a chance. I change my engine air filter every oil change, as it's cheap, and at 133K-kilometers and five years, no MAS replacement yet. (touching wood)
The one common mistake that I see with K&N filters is the elimination of the fresh air intake, leaving the filter exposed underhood. This will actually hurt power, as the engine breathes hot under-hood air. Not good.
I'm not "anti-K&N" as I used them for years in all sorts of performance applications. That said, I know that on most modern computer controlled cars, simply dropping a filter won't find HP like it once did. Old Chev small blocks were strangulated, and a new carb and honking big K&N usually found some power. Better to open up the head and exhaust at the same time for real gains.
1998 C230 "Black Betty"