There is a small, almost valve like piece on the thermostat. This needs to be pointing up otherwise the thermostat will not open all the way when it needs to. If you cannot find any other obvious problem, it could be that.
Fred 95 300TT SGP Stage..Who knows..lol Dynoed 539.4 RWHP, 481.2 Lbs. Torque Pump Gas @ 17 Lbs. of Boost NO NOS!!