I have a 2004 Grand Prix GTP. I haven't had any problems since I bought it in October last year. Now, it doesn't seem to want to stay running. If I'm at a stop light, the RPMs will flicker from 500 to about 2800. I have to keep one foot on the brake and one lightly on the gas to keep it running so it doesn't die. It occasionally acts like that while I'm driving at normal city and highway speeds. Replaced the MAF sensor, that didn't do anything. Can't figure out if I'm having a fuel delivery issue, or a spark issue. Maybe fuel pump, maybe distributor? Anyone have any ideas?