Looking at the pictures of your exhaust system I noticed the aftermarket oil pump cover that fits a spin-on filter. Note that most of these aftermarket items are fairly restrictive to oil flow and can reduce your oil pressure. Some are better than others, and some can be "blue printed" to provide less restriction.
It might be a good idea to hook up an oil pressure gauge and see what pressures you have at full hot engine operating temperatures. Idle should not be less than 20 psi and cruise at 3,000 RPM should not be less than 50 psi.
Original Post
