hello, i have a 1999 f150 5.4 4x4. i recently went on a trip and the truck started misfiring. first one cylinder, then two, then finally three. the trip was about 168 miles round trip, my concern is this. when i got back i took it to autozone and got my codes ran. i had a misfire on cylinder 2, 5 and 7. got three new packs five new boots and all eight new plugs. well i changed the plugs and on cylinder 2 there was oil on the plug along with metal shavings, it continues to miss on cylinder 2. does anyone know whats wrong with it? any advice or help is appreciated, thanks michael