It's got new plugs, all wires are good, each plug sparks, each cylinder fires.....I've checked my hoses, how do I check for vacuum leak at the manifold and throttle body? There is a hiss when i tap the throttle, can only be heard when you have the hood up. Sounds like it's coming from the manifold, but dunno how to check it and can't pinpoint it cuz of the shape...