One day my gf's car started misfiring bad (2.4L) so I started swaping parts between our cars to diagnose the problem. I figured out that when I bolted my ignition cover to her car it ran perfectly and when I put hers on my car it started misfiring as well. So we ordered a new one from the junk yard. Junkyard sent the wrong part.. from a quad4 but not a twin cam so the metal peice was a different shape but the coil packs and ignition module were the same. So I took her old metal cover and put the new ignition coils and ignition module on the old cover and it still has the same problem. This leads me to beleive there is something wrong with the metal cover plate itself??? But what in the world could go wrong with a metal plate???

check to make sure the ground for the left rear bolt is there, it sounds like the coil cover...