I have one in my '04 3.0, with no noticeable increase in intake honk. I got it for $39 online somewhere. I've been using K&N's on bikes and cars since the mid-70's. My experience has been that they do help MPG slightly ( ~.5 - 1.5%). I've also had Autothority CAI rigs (with conical K&N filters) on an '87 325is and a '96 328is and both were good for +1-2 mpg, better throttle response, a lovely intake noise, and a small seat-of-the-pants performance gain. YMMV