I removed the upper insulation pipe and the temperature has reached a maximum of 190F during 2 recent trips. It usually sits @ 186F for most of the time though. Seems like it there has to be a small opening even at low winter temperatures. I will be modifying the partial upper grille block to make it 100% sealed and more water resistant.
Mileage seems normal @ 47.5 MPG (114 miles with 2.4 gallons). Too early to say if it is the mod or just the nut behind the wheel making the necessary adjustments.
Stay tuned !