I'm confident that's not the case, because I didn't remove it when I pulled the lower intake, been the same thermostat for 10 years, and I know it works, I did a one hour run down check of the car, and watching with the lisle funnel I could see it open and close through the rising / dropping coolant volume. It is possible I need to move to a lower temperature thermostat, I'm still running the stock one, mostly because I do want the car at the appropriate operating temperature. The engine didn't feel all that hot, but the distributor felt the hottest of all the parts with the finger touch test. There's a lot of aluminum in there now to aid cooling, so nothing felt all that hot, i'm starting to look at aftermarket gauges now to make sure I have a better view of the engine vitals.