5-6 years I actially saw a "328iM3" badged, well... 328i.
Kinda interesting 'cause anyone who would actually care would also know its phony.
But it's your car. Do whatever makes you happy.
I'd be more inclined to de-badge an M3 or delete model type... (at $0, about the cheapest factory option on the 911) but that's just my preference.