hks bov makes car slower

i have a hks bov and i love the sound it makes, but it seems as though my 88 picks up a lot slower with it. when i use the stock bov, my car has more torque and boost. i already tightened the hks all the way down and its not helping. any advice will help me a lot. By the way, my cars rpm bounces up and down between 600 and 700 rpm and sometimes drops down as low as 500 rpm. i cant figure out what the problem is. have anyone have had the same problem? if so , what was it?

Sounds like a vac leak. Both of my MK3 friends are running HKS BOVs with no problems.

i already checked the vac lines, ill just keep on looking,