Oil pressure problems. Help!!!

[PavementScraperLSX]

2006 silverado oil pressure gauge is maxed out until you floor it (WOT), it then bottoms out. But wait it gets better goes back to 80psi when you let off the gas.  Oil sending unit? Or stepper motors in cluster?

[davester]

given that the needle sweeps the gauge (at least mostly from what you've written), I would say the problem is elsewhere, like the OPS, or wiring for it, or the actual oil pressure is fluctuating wildly for some reason.