We have a 2011 Subaru Legacy in the shop with a 36R engine for low oil pressure. 1 psi at idle and 27psi at 2500 rpm. Pulled the oil pan to inspect pickup screen to find that there is a very small orfice/relief valve trapped in the screen. I call local dealer to find where it belongs. Their seasoned tech of over 25 years is stumped. It is only about 6mm in diameter and maybe 13mm long. I figured i might throw out a hook in here!