Since the truck is used. Would you happen to have a spare engine laying around? If you do I would swap motors to see if the motor acts the same on the truck.
Your engine temps sound good. My 3.3 runs about 240. I would check to make sure your linkage and servos are acting the way they should. Make sure there's no bidding and battery is fully charged. I would set the engine back to factory settings and see if that helps.