Check out East Coast Injection Systems (ECIS) link attached. I picked up the e46 version and I love it!! Sounds great; much more "throaty" sound @ all revs, but, really growls above 3000 rpm..... A few guys with the long fender installed CAIs are now considering moving to a short ram CAI like ECIS because it sounds so much nicer and unlike a new exhaust, does not attract the wrong kind of attention (read POLICE here).... Do some searching around, I managed to find a company that was selling them for 50% off..... got mine for 50% off ECIS' listed price.....
Here's a link for a review of the ECIS CAI and the reason I went short ram vs long ram is similar..... Fear of injesting water with a long RAM.... had a buddy blow the motor on his 540i by injesting water through his long ram CAI.... http://www.emotors.ca/articles/43.aspx
Here's a link to ECIS' website..... You didn;t list the model yr, so..... I guessed..... http://www.ecisbmw.com/DMCart/produc...cat=252&page=1