I recently purchased an APEXi filter for my berk intake and I noticed that when I am around approximately 1500 RPM, there is a very odd hissing/rattling sound. Actually, it sounds exactly like a Ps2 does when you put a disc in. It didn't make that sound when the k&n filter was on, just the normal hiss around 2000 rpm. This is just a lot louder and different. I obviously double checked that everything was tight...any ideas?