If the valve on top of the Tstat opened, it indicates OVER heating... I believe that should normally be closed.

The test for the ECM temp sensor is EASY... but you would need an el cheapo Radio Shack ohmmeter to do so.

If on a cold start, your aux air valve is OPEN, i.e. strong vacuum at the hose end near the TB, and that vacuum goes away in like 5 minutes, then that valve is most likely OK.

If you are running hot enough for the valve on the T-stat to open, you've got other problems you need to find and resolve.

How's the condition of your radiator ?

C/YA!
Jeff