Hot at highway speeds

So my GVOD controller took a ****. I have a new one on order. This has however exposed a cooling issue.

My car has 4.56 gears with 28" tall tires. It has a GPS speedo so 55mph is 3,000 RPM.

Around town, at idle and slower speeds with fan on it's fine. 180ish.

On the highway it will go to 200, even approach 210. If I turn fans on it will come down slowly. Get into town and leave fans on the temp comes right down.

This was not an issue witht he GVOD and lower cruise RPm.

What would cause a temp increase at highway speeds when traveling at more RPm?