Well there is a piece on YouTube, they put in a cooler, used the pressure test port and tapped the drain hose into the oil pan: not hard but will using the port "short circuit" the pressure to the engine? As a pressure port you are not allowing any flow, but making it an outflow port bleeds off pressure since the cooler will not offer much resistance. the only way to test that would be have a second place to check pressure in the oil galley, is there another place to check that?