I'm not sure if it's related but I do know there is a TSB on about 3300 6.4L's built between certain dates. Apparently during testing of the engine by the engine builder (Navistar/International) they reversed the polarity on 3 injectors (1, 5, 7) and those injectors may fail. Some people had complained about rough driving, studdering, etc... Ford identified the vehicles and any of them unsold and still on the lot where put on hold till new injectors came and in were replaced. This is why my truck is still sitting at the dealer and not in my driveway. I don't know if this is also part of the flaming tail pipe trucks as well due to leaking injectors.
Bill