I actually plodded along in my research and found another thread here that said it tells the ECU to turn on the fuel pressure regulator. And I may have found a replacement from Yota Shop, woot!
If you have access to a local junkyard you might consider looking for mid 90's toyota's (corolla, camry, truck, 4 runner etc) and see if any of them have the same switch. Toyota will use different part #'s for the same part in different vehicles. I found the other two switch's/sensors (cold start injector & water temp sensor) for my 91 super cheap this way.
The water temp switch 89428-60060 tells the ECU when to fire the FPR VSV to control fuel pressure.
The connector housing is 90980–10197. About $4 from Toyota.
