Oil pressure gauge at 80

Because revving the motor makes the oil pump spin faster and therefore increases pressure. It should be stable and within specs when you are at cruising speed.

Just because it runs good is no reason to drive it into the ground. No oil pressure can ruin an engine fast. Hopefuly the reason no oil pressure is the sensor is bad, it's connection is corroded and thus bad. If mine I would take it to a shop and have them actually measure the oil pressure with a mechanical gauge. If no oil pressure that way, you know you have a serious problem. If the mechanical measurement is good, then you know that The sensor is bad, it's connection is bad, or the oil pressure light or ? gauge
is bed on the dash panel. Good luck.

You have low oil pressure which names that you sustained a high pressure of oil and now it's really low

The BCM doesn't control the oil gauge (or any gauge for that matter), chances are you have a defective oil pressure sending unit ON THE ENGINE..

Pull the sender out and install a universal oil pressure test gauge.

oil sending unit needs replacing. I just had the same issue with my 06 Tahoe.

It sounds like there is a problem with the oil pressure sending circuit. The oil pressure sender changes voltage according to the differences in oil pressure. If it is pegged all the way to the max, there may be a short (or open, depending on the way the circuit is designed). I would take it to a shop and have the oil pressure tested with a mechanical gauge first, just to be sure there isn't a problem with the relief valve on the oil pump. But if the oil pressure gauge isn't working properly, you won't know if there really is a problem with the oil pressure, and that could be catastrophic to the engine.

right around 40 psi at idel maybe just a little under

I agree with you, replace the oil pressure sending unit.

if its not a fuse check the speed sensor for the tach, and the oil pressure switch on the side of the engine block see if the lead came loose