brakes and idle

Does anyone have a clue on why my idle goes up when I put on the brakes in park? Could it be my booster or just a plain old vacuum leak?
Thanks Mike

how much does the rpm go up? You could be right about the booster. Does it make a hissing noise when you step on the pedal?

:banghead: It goes up a few hundred rpm's I didn't check it with a tach but its noticable and a little bank going in to gear. No there is no hissing and I checked hose and check valve all good :screwy: