I went through the same thing with my oil pressure. I showed 20 psi at hot idle, but had a friend put a mechanical gauge on it and he said i was actually almost at 30 psi at hot idle. At 3500 RPM, my gauge showed 60psi, the mechanical gauge showed almost 80psi. I replaced the oil pressure sensor and its a little more accurate now, but not much. I am thinking about installing an aftermarket mechanical oil pressure gauge just for my piece of mind.