Well, after I put all new Motorcraft COP's on the 4.6 I still had a CEL flashing under load. So after all new plugs and COP's, it's was "like what is next on the list". Keeping things simple I decided to go back and check the cylinder (#2) that kept showing up. Just for grins I decided to replace the Motorcraft spark plug with another one. Guess what??? After all the head banging it ended up being a faulty plug. Replaced with another new Motorcraft plug and all is well after a couple weeks. Lesson learned, don't overlook the most simple things.