For those of you who have ever cared about this, I’ve located the diode block that the Samurai uses to isolate the three large electrical loads that cause the ECM to increase the idle speed (lights, fan, tintop rear defroster). Maybe this wasn't a mystery, but both Search and the FSM were silent on where this beastie lives.
In the attached picture, the diodes are in that white nylon block in the center of the image. It’s hanging from the wiring harness that runs from the driver’s side kick panel across the dash to the cluster (?), running roughly between the LHS dash air vent (you can see the flex hose above the diode block, on its way to the vent) and the four squares molded into the lower left dash for switches (where the panel dimmer is).
From what I can tell, the block doesn’t unplug from the harness, but there seemed to be a way to pop it open if you wanted to.
My hope was that there would be an easy way to add diodes to it for additional electrical loads, like driving lights. From the looks of things, it will be easier to just tie into the ECM harness on the passenger side with discrete diodes (from Radio Shack).
I hope this helps someone!