The only real difference it will make is allow more filth to get into your engine. I saw a study on this once and the K&N filters better than a BMW filter for the first few hundred kilometers and then filters worse for the rest of its life.
Think about it... especially the 330i guys... you already have a 3-stage intake manifold, do you think your engine will run out of air at the high end??
The only guys who might see a little high-rpm advantage is guys with the "detuned" 325i and 323i powerplants. Even then, what, like half a horse power?