http://www.bimmerfile.com/2016/02/22...ng-the-bmw-m2/
quote:
The exhaust flap is closed at idle, in the lower speed range and nearly of the time when the car’s in COMFORT mode (the exception being under heavy load).
In SPORT and SPORT+ positions, the exhaust flap is fully open when the engine is idling while the vehicle is stationary and in the lower gears.
unquote