Was reading a thread by "scaryslow" and have had a similar problem. This was my experience and current issue. Symptoms can be similar between causes.

Some time ago my Regal GS had no power, would start and idle but not enough horsepower to move. If you tried to drive it the exhaust manifolds would get red hot. No codes. Was the harmonic balancer/crank sensor. Thought the CAT was clogged and replaced that first.

Next had a rough idle and hesitation and missfire. Cleaned the throttle body and sensors. Replaced one bad plug wire. Repaired vacuum leaks. now it idles smooth runs decent under moderate exceleration. Still misses on cylinder one (OBD code) under heavy exceleration or moderate exceleration at highway speeds. Have replaced fuel filter also.

Need suggestions on the remaining missfire issue.

Thanks in advance for helping out the new guy!