[bwood]

Check all the plastic line coming from and to the EVAP canister. I should be mounted up above the rear axle with a plastic tube from the gas tank that collects pressure/vapors from the tank and then there is a tube that goes all the way back up the front of the engine. Remove the plastic Vortec cover from the engine and look for a little green service cap. This is the service port for the EVAP system. Just under that port is a solenoid that opens and closed to allow the vapors from the system to be burned off through the intake. A cracked or broken line, a solenoid hung open or a damaged/missing component could cause a lean condition. I can remember discussion about a vent valve or check valve that can get rocks/debris in it and cause EVAP system issues. Unfortunately I can't find the posts about it.