The 5.4 3V heads were redesigned in late 2007; one of the upgrades was a change from the original 2 piece spark plugs to a new one piece design. The one piece plug is not backward compatible with the old 2 piece design. However; a stronger, laser welded 2 piece plug was released to service 1st Gen engines.Ahh, didn't see that posted. The 5.4L is a fine engine. Keep up with the maintenence and that motor will chug along forever. There are some upgrade to the sparkplugs I would look into. The upgraded plugs area one piece design rather than the two piece that woud break when you tried to remove them.