^^ That isn't their bov, theirs is all metal and you can see the piston from the outside.

 

This is what mine looks like I don't have any problems.

 

I have that same black dual discharge inline blowoff valve like you and it came with my inline pro kit...

 

Based in my knowlege this is the older style, I have the newer model shown on the website, click on my build and you can see detailed pics

 

When I tried the Greddy one I just ran a vac line straight to it from the intake manifold. It looks like you have it tee'd onto something else. How is yours routed?

 

why not get a bigger bov. maybe its just not venting enough? had this happen on a supra. the customer upgraded from stock turbos to a greddy t76 and had an old type-s bov. after the upgrade there was major compressor surge. it turns out the type-s couldn't flow enough so we put a type-r on and problem solved!