sounds like maybe wires.. the hud will resond faster than the dash... the evap sensor is on the back of the engine behind the supercharger around that alternator support. check the vacuum lines... and i cant recall what wires but if you use a mulitmeter you shoulde check the tps resistance to see if it is fine. the restance should steadly change as you move the throttle plate... also check for pinched wire harnesses... i had a big headake when my o2 sensor wire was against my exhaust manifold and melted the 4 wires in to a crispy gooo..