like i said in the topic if the check valve is going bad in the brake booster line could it affect the boost gauge like not make it read enough vaccuum cause my boost gauge is reading like -17 at a stop in idle but when im driving and let off the gas in gear it goes to -20 shouldnt it be -20 even at idle not -17???

 

I assume you tapped the brake booster line before the check valve. I was running my vac lines this weekend and almost cut my check valve in half. duh!

Your reading more vac with the car in gear and no throttle input and coasting because the throttle plate is closed, the engine is still going thru it's normal compression stages and so it's gotta pull that air from somewhere. Big rigs use that to help stop and slow when going down hills.

Your vac readings are actually low in gear and decelerating.

 

well actually my gauge is hooked up directly to my intake manifold i didnt tap into that big line

just dont know why my gauge is acting very slow and is only reading -17 at a stand still at idle sooo

it just goes into boost then back to vac just slowly not super fast like normal