Car overheating now.....

[99LS1Z28Jer]

Hi, I have a 99Z28/LS1 that just recently developed an issue. My car has 125,000 miles on it and it threw the P0405 code which is something about the EGR valve and voltage. At the same time this happened, my car has started to run hot. It would always warm up to 210 on the gauge and stay there, but at the same time the EGR issue happend, it would go to 210 for awhile, but then (usually when on the freeway) start creeping higher and fluctation some between 230-250 and never going back to 210.

I disconnected the EGR altogether but the temps still rise the same way.
Any ideas ? I thought maybe the EGR is sticking open even when closed, but I haven't really noticed any kind of rough idle/running conditions. Just the temps.

I thought the cooling system thermostat may have stuck closed, but that would be ruled out by the car heating to 210 and staying there awhile before creeping past that (usually takes 10 min at 210 before it goes over)

Thanks for any insight.
Car is pretty much stock as far as upgrades.

[crazy dave ls1]

fans are working?the egr is used at part throttle and light load to keep the combustion temp below 2500 degrees to prevent Nox.I'm not saying that wouldn't cause an overheat condition but I've never seen it happen.sure you dont have some other problem like a stopped up/partially blocked radiator or intermittent fan problem?I just got back from vacation at cedar point.great place yall got up there.