To keep a long story short, I found out by trial and error that an 89' corvette thermostat works on an 88' Turbo II. My FC was running hotter than normal even after flushing out the coolant and radiator. My Dad pointed out that I may have a bad thermostat. I ended up pulling it out and I did the old thermostat and boiling water test. Sure enough, my thermostat was opening at 190 degrees. The Haynes manual I have says its supposed to open between 177-183 degrees. My dad went into the garage and got his stock 89 vette thermostat to see which of ours would open first. His opened at 180. After looking at the two thermostats side by side, I noticed that the circumference and diameter size were the same. I knew kragen and autozone wasnt going to have an 88 FC thermostat for sale. I also knew that Mazda was closed on Sundays. So, I took a risk and threw the vette thermostat into the FC and it ran like a champ. Not to mention a whole lot cooler.