Must be a Vacuum leak right

[driftersilvia240sx]

Ok start up my rb, runs great !!! timing spot on
It pulls 19 lbs of vacuum at idle
now if i tap the brake kinda fast the vacuum tends to decrease to the point of it stalling...
Now ether i have major vacuum leak, bad booster what can cause this ???
i hate holidays i dont get to work on my car...
thoughts opions any one???

[stangimon]

Why don't you check out the brake booster check valve. Their made of hard plastic and have a tendency to crack. Pull it and blow on it to see if it works in one direction

[driftersilvia240sx]

ok before i start my car, ill push the brake pedal a few times til it gets hard...
Start car i feel the pedal go down. therefore there must be vacuum getting to the booster.
still doesnt break like it should :/ and vacuum can go from -19 to -14,-15 when applied
I hear no hissing from the booster any other ideas ??? i ordered the check valve just because from nissan looks a little sketchy..

[Carl H]

check valve backwards?
brake pedal should get lighter with engine vac applied...not harder.