I have a Titan 370 that suddenly developed oil pressure problems. Is there a picture where I can plumb in a mechanical oil pressure gauge on the back of the engine? I have an inverted oil system and hope I didn't already use the fitting. My pressure has run steady for 250 hours at 78 to 80. Suddenly, it started going down when I retarded the throttle. I thought it was a ground issue and changed the sender, Garmin G3X, and re-grounded the wire. No help. It got down to 16 psi at idle landing then was 65 taxiing in. It has been acting up the last 50 hours. I'd like to put a mechanical gauge on to verify. Thanks, Chris