SPLICE AND SOLDER IT WITH HEAT SHRINK. no crimps.

you want the best electrical connection you can get.

Sal,

OK, I understand now how the AC relay interacts with the starting system. The DME and it's relay are a non-factor, as my ICV hums away. Fuel and spark are definitely not the issue. Been there, done that. ;)

I've narrowed it down to crappy wiring from the ignition switch into the old, crappy aftermarket alarm.

I'm just a shadetree wrench with middling skills and fewer auto electric skills. I'm not very good at reading schematics, which is why I enlisted my certified wrench buddy. He can decipher this stuff and write it down in crayon for me.

I'm probably going to jinx myself for writing this: the last two days after unraveling the unholy mess of wires at the ignition switch, I've had zero "no start" issues. I'm leaving everything hanging out now because I'm planning on going in and following T77911s's advice on cleaning up the mess correctly (with an eye towards a new alarm or complete delete), and because my issue seems to be behaving at this particular moment.

You guys have been a great help. Your advice has helped me wrap my head around the issue much better.

That yellow wire on pin 50 of ignition switch needs to be intact all the way back to the starter. This is the wire that is often cut/spliced with after market alarms. Just really look at all the wires at the ign switch and fix them up.