Problem started immediately after 80k maintenance. Eventually replaced one very badly burned plug (cylinder 2). Ran ok for about 2 weeks & started misfiring again. Ignition pack on that same cylinder was bad. Replaced but now the misfiring is much worse - cold start is very rough! Since Computer indicated cylinder 2 problem - that's where the bad plug (new at 80k service) had been and ignition pack was damaged, Dealership now says could be carbon coked or fuel injector. I want all new plug installed and ignition packs checked on remaining cylinders before having them look for anything else. 80k service was VERY expensive and they will charge for further checking. NO problems before I took it in - good mileage, smooth running. Now the mileage is way off and engine runs rough. HELP!