Cody you are correct but, I have had a friend where there was no thermostat and his car wouldnt go past 155.Only when he beat the living shit out of his car it would go to 200+.

Now as for the being to cold post and the being too rich post.If your head intake and block do not meet a certain tempature then the combution chamber will actually not fire the fuel as fast as needed to.Fuel (gasoline) has different flash points and when spark is mixed with heat it will reach its flashpoint and BOOM you have power.If your car was sitting at 160 or lower it seems to just be using fuel and igniting some of it that pass's because the motor is not at rec. temp.

To me when the 5.0 motor runs about 190f with thermostat open that is more effective and has the most power at that temp.

Hope this makes a little sense