[BNaylor]

You're welcome.

I would do the flush first and then go from there. You can tell when the thermostat opens by watching the engine temperature at the temp gauge at the IP. If it doesn't open or open at the right time then your operating temperature will be high, probably above 1/2 scale or more on the IP gauge. Also, the PCM module will trigger a P0128 DTC if the thermostat is not opening properly or too slowly. The other scenario is the thermostat is staying open so engine warmup will take longer but the IP temp gauge will read low around 1/4 scale or less. The other way to test a thermostat is to remove it and put in into a pan of boiling water on the stove with a temperature indicator and see when it opens. Stock should be fully open at 195 degrees.