[AzTumbleweed]

Probably the 'Purge Solenoid'. Follow the vacuum line and it should go up and mount under the throttle body. Disconnect this line at the solenoid and plug it up with something to see if it makes the problem stop. The other line should go to the charcoal cannister. That's a black, plastic box under the battery. This is emission control stuff but I guess if the solenoid were stuck open it would be like a vacuum leak and make your car run bad.