My car calls for a 191 thermostat, I wanted to know if it would hurt to put a165 thermostat into a2007
This could hurt your fuel economy by making the engine run rich.
On an older car, this would have helped reduce the engine temp by opening the Tstat sooner. Current computer controlled engines determine the mixture needed based on several factors - one being engine temp. FOR is correct. Putting in the lower temp Tstat will confuse it and enrich the mixture to compensate.