Well I swapped in a new brake booster from a GSR into my 95 CX 1.5L car. Now my engine at idle is constantly revving and dropping between 1-1.5 rpms on its own. I know its caused by the brake booster and the vacuum hose connecting it to the intake manifold. If I pinch the hose so that air has a more difficult time flowing, the problem goes away. Anybody have any experiences like this and/or know a way to permanently get rid of it? Thanks.

 

I think you forgot to put the check valve back on the booster line.

 

Nope, check valve is on there and functional