Oil pressure dropping

[carco]

Ok Update, on inframe. Runs better, smoother, still pulls good have not checked fuel mileage appears a bit better but need to run figures.
All parts were Cummins, including dampener, and reman head. My shop did the inframe tried to watch everything only our second ISX. The first was last summer in a T800 dump truck, still running everyday driver bought it from company and loves it!
My low oil pressure problem is still there,,, however a manual pressure check has revealed oil pressure is good. @ 1600 high idle no load 150 degree coolant and 150 degree oil is 44PSI at idle 34-35psi! truck had been driven, parked and once cooled somewhat today we plumbed in the manual gauge which is why, by coincidence, oil and coolant temps matched closely at 150 degrees. So believe a hot idle at 200+ degrees will still prove to show good pressures.

So ECM or wireing connection may be corroded at new sending unit or at ECM or inside ECM or inside wire. The ECM via laptop shows same pressures as the dash gauge therefor I believe the problem to be between the sending unit to ECM or in ECM. Thoughts???