My 2005 F150 FX4 5.4 is in the shop for head repair and the shop told me they are going to install Champion 515 in place of the motorcraft presently in it. They apparently, according to the shop tech, have had way much better luck with the Champions as opposed to the motorcraft. The engine (truck) has 114500 miles on it. I was going to install some E-3s that I had but was advised against it. I wonder why? The E-3 is a one piece as opposed to the dreaded 2 piece. Any suggestions would be greatly appreciated.