Just installed AFE's M3 Replacement air filter to get 6-10 more horses out of my M3. I also installed their Dynamic Air Scoop which took all of 30 minutes - would have taken 15 if the front grill would have come out easier. But wow I can hear the air sucking from the intake on the hood. Too bad every time I want to fully test it could involve a police officer. I called them up and the car is going on the dyno next week to see what the dynamic air scoop adds to hp
They also have a carbon fibre air box under development that makes use of the other hood vent.