Possiblilty one, you got a faulty thermostat. Any part can be bad right out of the box. (I had a new, Gates serpentine belt fail and strand me 50 miles after replacement! The new-new Gates has gone 10,000 miles and is still good!)

Possibility two, incorrect installation. Upside-down so it doesn't open correctly? (I don't know if it's possible on this motor, but it was possible on some domestic engines.) Gasket sealer partially blocking the thermostat?

Possibility three, blocked or collapsed suction hose reducing circulation. Coincidence, not related to thermostat replacement?

Possibility four, incorrectly calibrated temperature gage/sending unit, so that 95 is 80 and 105 is 90.

One, two and three require attention soon, while four is the best since it can be fixed but isn't a real problem.

BCingU, Jim