With aluminum heads you should be running a 160-180 thermostat. Yes the water temps will be higher partly do to heat transfer of the heads but also increase in compression causes more heat. I recommend changing water pump if that’s not new. I always drill a small hole in my thermostats. To ensure water flow and limit possibility of air trap. One last thing. Some of these newer heads actually require a MLS gasket. I just went through this problem on a set of RHS heads. Even though the website for rhs said felpro ok. The RA finish is actually cut to use a MLS GASKET. The gasket never sealed against the head So far no more issues with over heating.