My theory is that it's function is not to perform like a vent it just so happens air comes out of it when not at full throttle. It is strictly there to provide enough air intake at full throttle. I also think that BMW did enough research to provide enough intakes in this car for air to get in. Therefore adding more intake spots or scoops or anything similar is a waste. You're going to get to a major restriction at the air filter and then through the rest of the intake into the cylinders. If the car wasn't getting all the air it needed don't you think BMW would've just put a bigger hole in the hood?? Does anyone really think BMW just released a ///M car that is starved of air? I'm willing to bet the only way you will get more air into the combustion chamber is to add some sort of FI that physically squeezes/pushes more air not only through the filter but all the way into the cylinders.
I have no evidence to support my theory, but just find it very strange that with all the R&D that goes into these cars that they would somehow starve it of air.