Check the viscosity of the oil. 15W40 is a great all season oil. Look in the oil
fill hole with the engine running and see if you can see the oil being sprayed
on the cam lobes. If you have good flow, hook up a manual oil pressure gauge to
the oil pressure sender port and check actual pressure cold and hot. The other
thing to look for is the cam oiler pipe under the valve cover. The rearmost 10mm
bolt likes to loosen up with time. If the oiler is too loose, you will lose oil
pressure. We loctite the bolt whenever we have to pop the valve cover.