Keep in mind that the thermostat sensor should be measuring radiator core temp. This will hold you engine temp a bit higher that a fan clutch ( by 5 - 10 degrees). On many engines keeping the operating temp at 190 -200 gives the best performance with the lowest emissions. I dont know about our tt engines, as they create more heat and work much harder than an n/a. I have always set mine using a laser thermometer on the cylinder head while adjusting the thermostat set point. This way it is essentially calibrated to the engines needs and not the radiator core temp. Hope that this helps.
