I recently purchased and installed the aFe Intake Stage 2 54-11012 BMW 325i/328i/330i. Price from AFE direct is on extreme sale. I paid 260ish. Car as extreme sound difference, but its only there when you want it to be 3500+ = awesome sound. 3500> not noticeable at all. I am very satisfied. Power difference w/sprint booster makes for a really dramatically different driving experience.
Bottom line: I am not concerned with my engine receiving enough air.