The M3 responds very well to just the basic tuning like metal CATS, exhaust, intake and well developed ECU remap.
There are already claims and what I believe to be genuine dyno graphs which show 460+bhp.
In the real sense, that's what most sc'd E46's make if they want to stay reliable.
The E46 never responded that well. 15bhp from an ECU tune was the max in the real world. Intake modifications never worked unless you were looking at larger intake volume based plenums and exhausts added around 5-7bhp on a good day.
I am sure we'll get loads of compressor kits for the new M3 but I won't be offering them without plenty of durability testing.
It's easy to get big power but for how long?