Thing is, they don't seem to be able to answer. I also had to inform them a new bumper is needed when installing M perf exhaust (same as you have).
The diffuser I'm talking about is partno 51192412406 Rear diffusor, matt black that goes on the M performance bumper. Concerned the folding towbar will damage the "fins". Searching different sites provides little help as I have seen some state it's not compatible and some indicate it works.
But if i understand this spec on RealOEM the matte black diffusor should work (see section 8-10):
http://www.realoem.com/bmw/enUS/show...17#51192412406
Correct?