Just dont buy a F150 with a Triton 5.4liter engine. Ford has serious issues with these engines. I have a friend who learned the hard way. Had one and started having problems with a couple cylinders. rough idle, bad gas mpg, etc. he traded it in a new F150 with a triton 5.4, 3 years into his new truck, same problem. He traded in on a Subaru, he says he will never buy a ford truck again.
5.4 2 valves are good to go. The 3 valve are a nightmare. I learned the hard way too.