I have a 1999 GT. Recently it has stopped idling. The car will run great if I keep my foot on the gas. Once I take my foot off...the rpm's fall fast. I don't have any check engine lights or anything else showing up. The car is stock except the mufflers, but I've driven it 15,000 miles since those were added. I have recently tuned it up (new oil, oil filter, air filter, spark plugs, injector cleaner..) but it is no better. I'm a full-time college student, with college student income, so any help would be greatly appreciated.