Ohh so you mean a blow off valve... Mounts to the turbo- intake pipe... If your after just a sound over performance as stated, run a pod with no valve and you will get compressor surge like a rally car... Rally cars don't run BOVs because they run antilag.
If you want performance run a valve because otherwise the excess pressure in the intake pipe when the throttle body butterfly closes when your off the gas slows the compressor wheel on the turbo and increases lag/ spool time when your back on the gas...
A valve will also cause the car to run little more rich, but wont your guys emissions laws make a atmosphere venting valve illegal?