I can't remember on the 5.4L but there maybe a plug on the backside of the head (should be T30 torx head plug with a o-ring.) Like i said I don't know if the 5.4 has it or not.. Maybe something to look into. I would say no on the pin hole theory but I'm not gonna swear on it just because I've seen motors do crazy things. Can you take a picture of it?