Most people don't even realize the 4.6 and 5.4 share a lot of parts. The blocks, rods and timing chains are the only real big differences and that isn't enough to make one a lemon over the other. Ford slapped the 3 valve heads and cam phasers on the 5.4 first,so it got to be the lab rat with them. My F150 in the picture above is still going strong with its 5.4 and it's the first year model of that body style and yes, I changed the plugs myself, without any problems!