FSM states it should be at least 11 PSI. As you are aware the oil pressure increases with the engine RPM. So next question is what is your oil pressure when the lifters start and stop ticking? The oil pressure sending units in these cars aren't that reliable. How many miles are on the engine? You might want to confirm the oil pressure with a mechanical gauge to confirmed the oil pump is functioning properly. As a side note these cars are notorious for lifter tick. Hope this helps