I have a 96 Mystique that was making a hell of a racket, it turned out that the timing belt was hitting the inside of the cover. I had to replace the tensioner and the timing belt (150,000km's). Runs great now. Just take off the cover and start it up, you'll see it. Good Luck.

96 Mystique, 2.0L ATX, tinted windows Head unit: Premier DEH-840MP Front Speakers: Phoenix Gold 5x7's Rear Spreakers: Pioneer 6x8's Sub: 2 12" Pioneer Premier TS-W1240C's Amp: Pioneer GM-X922