So your truck is fixed now? What did they do? Motorcraft or Autolite are the only plugs that I know of for the 3v V10.

 

There is also a new Company called Brisk that makes a plug for the 3 valve head. It has a conventional ground electrode, but they are pricey, and in the Mustang world, nobody has had good luck with them. Your best bet is to stick with the Motorcraft ones.

 

The conclusion is that the engine is so sensitive to addatives, it impairs the plugs from firing. They say I cannot put anything in the gas. The last plugs had a reddish tint on the ceramic which was from the octane boost, this caused the problem. New plugs run good. Will see how long this lasts.