Ah, i see... IMO, you're only going to look like a fake M3 if you put ///M badges on your car... but it's all your opinion i guess. M3 rep bumper is not too far off though...
I vote you should get the F10 M5 bumper molded onto your ride... ^__^ would also look sick.
I have 20x10.5 in rear (i forget the offset off the top of my head) and i still have a bit of fender room so i don't think the fender itself will be the issue, but more like what you will rub against on the suspension side.
WTB: 3 Stage Intake Manifold and components - PM me your asking price.