Brief recap of events: At around 99k miles I developed a miss, that got progressively worse, and at around 101k miles I replaced all 8. 7 came out ok, with screeching and noises. 1 broke in 3 pieces, and I had to drill and tap the head. Installed Champions 7989, and coated them with nickel anti-sieze. Last month at around 132k miles, I pulled them all out and recoated them again (most of it was gone). All was good for about 3 weeks or so. Yesterday, I went to work and back just driving on 7 cylinders. Found # 4 cylinder not working. Swapped the plug and the coil to # 2, and #4 was ok now, # 2 was missing so I knew it has to be either coil or plug. I still had the original plugs in the garage, so i just screw in the old Motorcraft, and it's fine. This morning while driving to work, ocasionaly it would miss just a little, so either the old Motorctaft is missing, or another Champion is on its last leg. I decided to replace all 8 again, and will go with Motorcraft. Can I use Motorcraft SP515 ? Nor realy happy with Champions lasting only 32k miles.