Jared- I agree with diesel31....you might be running too soft of an insert. I always run Yokomo firm inserts in all of my 138G tire's. With the track temps you posted I would drop down to the regular 138G's with a yokomo firm insert. The GF should kick in at track temps above 125. It also depends on your driving style. If you pitch the car into the corners the tire's will heat up quicker so the harder (GF) would be the tire of choice for those conditions.