"Bosch and Regina IACs are NOT interchangeable. According to the FAQ, Bosch IACs have 3 prongs on the harness, whereas Regina IACs only have 2 prongs with a constant 12V supplied to it."
• The '93 greenbook diagrams for LH 2.4 and Regina show both IACs as being the 2-pin type. The circuitry appears identical too:
>+12V to pin 1 (BL/Y wire) when the FI System relay energizes at Key On II
>Ground wire (Red/Black) to ECU pin 33.

Maybe the FAC is referring to LH 2.2, which did use the 3-pin IAC.

"I hooked up a multimeter to the IAC lead and as far as I could tell, the 12V is constant, regardless of whether the engine is actually idling, or being revved. This strikes me as sort of odd, because that would seem to indicate that the IAC valve is ALWAYS open, and if that is the case, why even bother having an IAC motor/valve???"
• I'd guess that the ECU can pulse the ground side, and thus control the IAC opening, assuming it's spring-loaded in one direction. Maybe Art Benstein, or someone else who really knows, can confirm or deny this.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.