Lately I have come up with a vacuum issue that I haven't been able to figure out.....At idle I am pulling about 26in/hg and on deceleration I almost bury the gauge to 30 in. The car also flutters between 600 and 800 rpm up down pretty fast...it almost sounds like a cam. When I drive the car it runs just fine and I hold 9 psi all the way to red line so I'm thinking it cant be a leak anywhere. The strangest part is when I unhook a vacuum source like to my bov, the car idles perfect and goes right to 20 in/hg. I have my blow off valve and boost gauge run off the back of the intake manifold from the small nipple by the IAT sensor and the big vacuum nipple on the front next to the fpr line blocked off with a bolt in the hose.

any ideas?

 

sounds like a really small vacuum leak in the intake track someplace form the TB to the head. to a boost leak test. from the compressor housing and find out.. and then on yout TB to narrow it down. make your own from a hardware store under 20 bucks.