So what were the results of the mechanical gauge you said you were going to run? I'm willing to bet your pressures are just fine. My 97 TJ used to do the same thing. The oil pressure sending unit and dash gauge are known to be terribly inaccurate.
"We are what we repeatedly do. Excellence, then, is not an act, but a habit." Aristotle
Yes, there was a new oil pump installed. It was an enginetech pump. Before putting the engine into the truck. I primed the oil pump and there was goof flow coming out of the oil filter hole. I then tightened up the oil filter to continue priming the oil and the drill wound up stopping when the pressure built up.
I sent the block out to a machine shop. Standard rod/main beraings and .020on the cylinders. They pressure checked the block and that came back fine.
Another thing worth mentioning is that the engine oil is very clean. It's not dirty at all.
The reason I asked about the oil pump was you said "when we were driving and we were making a left turn, the engine was idling and the psi went to around 15 directly to 0psi."
When you installed the oil pump was the pickup tube securly installed in the pump body? Did you install a gasket between the pump and the block, and torque the attach bolts down? Was the oil pump flush with the block at its mount point when it was securely installed?
You also said "continue priming the oil and the drill wound up stopping when the pressure built up." What drill motor did you use? I used a 120 volt/7.0 amp drill motor and it didn't stop. It slowed down some when the pump started pumping but it didn't 'stop'.
You did install a standard flow oil pump didn't you?