5.7 v8 No I mag

[jrsick]

The difficulty here is that there are no stated limits for high oil pressure.
Are you seeing increase in engine temps? The concern with high oil pressure is poor lubrication.
The service manual lists 4 causes of high oil pressure: thick oil, defective gauge/sender, restricted oil passages, and oil pump relief valve stuck closed. You have checked the first two, so now I recommend you check the last two causes.
Replace the pressure relief valve. I believe there are two in the system, but only one you can access. If that doesn't fix your problem then we move to addressing sludge in oil. Since the high reading started suddenly, you should troubleshoot every possibility.
Also, you may want to go onto some LS1 forums and discuss oil pressure with that group. These are hard core engine guys who have been running 5.7s for years.