I have a 5.4 L that I am getting ready to change the plugs in and had heard the storys of the plugs being a nightmare to get out so I talked to my father-in-law and brother-in-law they run a auto machine shop and ask the best way to take them out here is what they told me. First get the motor to operating temp then start on the back cylinders when you get the plug wire off spray the pulg with WD-40 or something like it, tighten the plug just a little bit not to much or you will stripthe threads out, then back it out. Check to make sure that you did not pull the threads out if so then you will need to put a healcoil in to fix it. That is a whole new set of problems and tools needed to fix. My brother-in-law said if someone comes to the shop that wants the plugs changed he charges $2,000 if it is a 2004 and up 5.4L due to having to pull the head to fix these plung when they break off. He did say there is a tool to get those broken plugs out but it does not always work. He said overhalf of the $2,000 is for parts.