My fans never come on in 2000 GT, but my gauge reads about 160 to 180. Did the same things you have done so I am pretty sure you just got a bad gauge. One question I do have, what temp should the car run to get the best gas mileage? One thing I did to my GT is get a cold air intake and that made my gas mileage worse. I have a 2002 GTP that's gets much better gas mileage than the GT