Ok, you said that you removed the stock BOV, do you have an aftermarket one on there? If not, that's the purpose of the blow off valve,to blow off the excess intake charge when your throttle plate is closed (ie: when you let off the gas). If you haven't got a BOV on there then you're more than likely getting compressor surge against the throttle plate. If you DO have an aftermarket BOV on there, then disregard everything I just typed.
-Andy