no filter will get you much more noise. Im assuming your intake is similar to the N52 which I have. You can get some more noise by getting rid of the intake muffler Theres a DIY for that somewhere. also you can do something like DJApex did. Lookup his eurobox mod thread for a DIY.
2007 TiAg 328xi: AA Tune, AFE intake, Full exhaust, 335xi Brakes, H&R RSB, UUC FSB, H&R Sports, Billy Sports...BBS SR 17x8
1985 Gazelle Beige 325e: Poly everything, e24 3.25 LSD, 225 lb weight reduction, Corbeau FX1, Shifter machined by me, roll bar, harness, all the other goodies. My "Racecar"...15x7 BBS RA