Have you tried running 5W30 instead of 5W20. The earlier 4Vs used 5W30. Ford changed to 5W20 later to comply with CAFE standards: not because it was better for your engine. I have run 5W30 in mine almost since the beginning (original owner) and have never had a lubrication issue. All of my original bearings and cam journals looked great when I had it apart at 40K miles.