I would change the thermostat just to be safe, put what you want in there, I use a 160 but I am carbed so maybe a 180 for FI, I ran that when I was FI and it worked good. Check to make sure your fan is on, if it is great if not, you can straight wire it temporarily to see if that is it, then move on to why it is not working, if it is working, check the radiator for grass and bugs or whatever and go to car was and blow the fins out if they are gunked up. Also, after your thermostat opens up, make sure the water is flowing by looking in the radiator (open it first before running). If it is not at all maybe your water pump is bad if it is barely flowing maybe the radiator cores are clogged and it's time for a radiator.