Running Hot on the Highway

They're are only 3 reasons that come to mind that would make it run warmer at hwy speeds than at idle or slower traffic speeds. First is a restriction on the flow thru the radiator, this usually happens on a older partially block radiator. You say yours is new so? second is the water is not staying in the radiator long enough to transfer the heat to the air, Need to run a 180 degree thermostats, yours maybe flowing to much water. Third is your motor is running lean. Don't rely on the throttle response for it not running lean. A engine runs it's best at a leaner than rich condition, especially throttle response. My 2 Penny's