Something I do know. If an oil filter does not have a good "flow", than this can cause a drop in oil pressure. You can stuff what ever you want in a filter to "grab" junk, but if the oil cannot go back into the system, well then, you have bad flow. The smaller the "mesh" the more it will grab, but the slower it will flow. If the bad filter is on, and you raced the engine, does the pressure come back up? If it does, that is because it is being forced = bad flow.