"...I will pull the coolant temp sensor off the 1986 if you tell me they are compatible bewteen the 2 years."
NO, they are not compatible. The '86 is a single element sensor "feeding" info to Ignition and FI ecu's. The later sensor has TWO elements, one for ignition and one for FI. Regina and Bosch LH2.4 both use this later temp sensor.

"Do you know if an Internet resource that has a compreshensive operational explanation of the Regina Systems in our Volvos ?"

I don't, but I see Regina as mostly the same as Bosch, just using a different way of sensing fuel needs, a different type of O2 sensor, and a different ECU to analyze input signals and control fuel delivery. In fact, the ECU output pins and wiring are identical to the Bosch LH2.4 ECU except for a couple of pins.
IMO, it's simple and reliable system, despite rumors and myths based mainly on the fact that it's "not Bosch" and thus unfamiliar to most of the old dogs—as it was to me nearly 4 years ago.(No operational problems in that 4 years.)


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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.