If you want a loud BOV sound get a hard intake pipe and a K&N FIPK...part of the reason you don't hear your BOV is there's a pipe inside your intake pipe which routes your BOV recirc way down into the intake track and muffles the shit out of it. That and the airbox takes out the rest of the noise. If you get a hard pipe and an open filter then put in a Greddy Type S (or the new RS) and recirculate it you'll still hear the sound but not screw up your AF ratio.