i have a 97 s420 the car idles decent but rough. It barley moves past 40mph and never faster than 50. The car shifts perfect so its not stuck in a high gear. The wiring harness seams fine not brittle at all. It has a check engine light on which when put on a code reader said misfire. My question is what could be wrong with it? And if one cylinder was misfiring could it cause the car to run like that. petal to the floor top speed was 40 and then 50 down hill. the tach showed the engine was about 1000 rpms from redline.