I took a quick look at the posts so far and do recall anyone suggesting installing "
oil restrictors" in rocker
oil galley in the heads (if you have restrictors check that they are still installed and possibly change to smaller ones). This should increase pressure in the system. Another place to check is the
oil pick-up to make sure it is sealing to the pump and that it doesn't have any cracks or leaks.
Just more long shots.........good luck,
Mike