Does the fan always run on HIGH. The fan is not ON/OFF, it is low speed, high speed, as you need air flow over the CAC (Charge Air Cooler-- aka Inter-cooler, aka After-cooler) to keep intake manifold temperatures where they should be.
And, fan speed should not really be related to coolant temperature except under heavy load conditions.
Said another way, the thermostat is what sends coolant to the radiator (or not). Sure, lots of air flow will cool coolant returning to the engine from the radiator just as will use of the dash heater, but that just means the thermostat sends less coolant to the radiator.
If you get a chance, pull into a rest area on a cool day, flat or descending grade. Leave the engine running-- use cruise to set to fast idle. Best to use a strobe tach to check fan speed OR "feel the air flow"/listen to air flow.
Do the same after a long hard upgrade, particularly at high ambient temperatures.
Any difference in fan speed?
Do the same after a long