I had a 160* unit in and brought it to the shop to be tuned. Mechanic wants to have the 195 piece in to help the computer run right. Will it only benefit emmissions and hurt performance or help?
If your cooling system is functioning correctly it will not over heat. You are fine. Don't be so concerned with this change. The car's were design and built to run with that t-stat and I'd be suprised if you punished it worse than Ford did in development testing. Have you ever seen the heat soak test Ford does? It's brutal.
Unless your car is bone stock and every component is new, I would run the cooler stat (180*F) if you are running too hot for your liking right now. If your system is overbuilt, the 195 will do just fine. The puter needs to see coolant temps of ~178* to enter total CL fuel trim.
I think what Mike was trying to say is ... just not to sweat it. If you want to change it later, you always can. It will run fine, and you might not even notice the difference, so have fun with some other stuff.