proper operating temp. for a 93 GA 3.3 ?

a few months ago, i posted about my car not running as well when it would be hot outside, or when the car would get hot. It never over heats though. Anyhow, according to the temp gauge, when the car is running as it should be, the temp is about 130 degrees. When the car doesnt run as well, the temp is about 160-170 degrees. (again, all of this is estimated by using the temperature gauge on my dash.) Sometimes if i leave the vent turned on & set to cool, it will keep the car at about 130 degrees. So, i was if there would be anything i could use to keep the car at a good running temp without using the vent? or do i need a new thermostat? anythin would be appreciated, thanks.

'93 GA SE 3.3
[coolant and waterpump new]

sounds like a bad t-stat or radiator. I think your approximations of temp are a little low though, most cars run between 185-215 degrees when warmed up.