I own a 2000 mystique just came back from a trip to Minnesota on the way home check engine light came on I figured no big deal this has happened to me before due to the gas cap not being put back on right. about 900 miles into my trip the car starts chugging on any incline i.e on ramps ect. got home by the grace of Luck had a mechanic look at it and he said I need a new catyalitic converter he checked into prices and said this would run me almost 1,000 bucks. called Mercury to see what they would charge for a new converter and I almost fell over they quoted me $1,800.. well in the mean time my timing belt now went out cost me $350 bucks to get that replaced. needed the car to get to work so we just took off the converter till I can get the cash to replace it. and low and behold the check engine light is still on darn pesky thing lol