My 2000 GT has been having some wierd engine problems. Sometimes when I would be idling at a light it would almost stall on me. the rpm's will drop to below 500 then spike to almost 1000. Sometimes it would even make my car jump a foot or too, even if my foot is on the brake. I thought it was bad gas so I put some fuel injecotr cleaner and 93 octane gas in it to see if that was the case, but it still happens.....