I have a 95 Mystique with the 2.5 duratec. At about 60-70 KM hr I get a surging or hesitation like the car is mis firing or something? Below that speed its ok, and above that speed its also ok. If I throtlle down it has lots of pull...but if I feather the throttle in that 60-70km area it hesitates? I can't figure if its the transmision or the engine...but I think its the engine.The car kind of chugs like if that is a good description of what its doing. I put new Bosch Platinum plugs in the car as I have only had it a month...but it also did it before I replaced the plugs once or twice as well. I installed a new runner control valve as well. I have no check eng lights on or anything like that. It just does that surging like or missing in under 80km more like 60-80 km area.
