Idles High on 2001 Pontiac Grand Prix GTP

car revs high sportatically when idling, periodically stalls when in park. i had a mechanic check and they found a faulty seal that they thought was letting air into the fuel. this seemed to be fixed for about a week but has started again. also the enginge light comes on when it is wet out and since we have had snow for the last couple months im not sure if the two are related

Asked by for the 2001 Pontiac Grand Prix GTP
have the TPS checked = throttle position sensor