Upgrading Ati by pass valve?

I have a stock Ati by pass valve that came with my 8# kit. Now that I am pulling for 12# do I have to change the spring in the by pass valve? I just finished building my 383 and pullied it to 12#, and I am getting a whistling sound at 1500-3000rpms. Only when driving down the street. I posted this and another member said it could be the by pass valve. Which makes very good sense, but I don't recall any one ever mentioning this when they do a pulley swap. All Iac and tps values are good on my throttle body so I don't it is that.What do you guys think? Any info would be great. Thanks.........John

That member would be me. Did you do that tape trick i told you to do? A 3rd gen buddy has had issues and upgraded to 2 MONDO BPV (Race versions) to fix this issue, along with back-spinning the blower impeller. He has a Bowtie 383 stroker w/ AFR 210s ported and an F1R procharger. Running about 20# of boost.

Ya, I tried the tape thing(I think). I put a piece a duct tape on the top of the BPV. It didn't blow off. You mentioned "put a strip across the opening". What exactly did you mean? Since I have mine plumbed back into the intake, you want me to pull that apart or did I do it right? Anyways it is still whislting. Please let me know.Thanks....John

heh, sorry i should have more detailed.

Put some tape, or anything really... infront of the BPV to simply change the way the air exits the BPV, don't block it off... puting something infront of it.. even just 1 of your fingers changes the airflow and will stop the whistling if its coming from the BPV. Otherwise the only thing i've heard of is a boost leak in a line somewhere or a Throttle body issue. BBK mainly.

So, the inlet side of the BPV or the exit side? Sorry, for the confusion. Thanks again...John

outlet.

I'll try that. Thanks again.....John