International with dt466 stumping all mechanics

I have a 2006 international 7400 with dt466 pre def. Truck has 260k miles. About 1 month ago truck started missing. Mechanic said 1 injector bad and one marginal. Mechanic replaced all injectors and did valve adjustment.

Day 1 of running with new injectors we are overheating, but only on the highway. If we run in the city all day we never get hot. If we run on the highway flat with tailwind no overheating, however headwind, or up and over overpasses, and running over 65mph and the temp starts climbing.

Once the temp hits about 225 the turbo waste gate opens, the truck power limits the truck to about 45 miles per hour, and the truck will through an engine code. If we cycle the key while running down the road and in neutral the code goes away and we are back at full power again.
At first we suspected the egr valve as it was plugged and dirty, however no change after replacing it.

Coolant has been flushed, radiator has been cleaned, belt has been changed, viscus fan clutch feels stiff and appears to resist spinning as it should.

Fuel mileage has increase slightly since replacing the injectors. Truck had been smoking since purchasing it at about 220k miles, smoke went away with new injectors.

Prior to replacing injectors no issues.

Codes we have seen are icp too high/low
throttle peddle out of range

We also noticed while scanning the truck that the vgt was showing -500, a strange reading.
The vgt does bounce when the key it cycled so it appears to be freely operating. 3 experienced mechanics have looked at it. None of them have been able to recalibrate the vgt with their computers for some reason.

We use the truck daily in town and it runs great. When on the highway if the temp starts to climb we let off the peddle and the temp will come down.

Any and all suggestions appreciated. I suspect it's related to the injector swap, but at this point I have one mechanic saying replace the wiring harness, one saying try a fan clutch and one suggesting a new water pump. I don't really want to throw parts at it like that.