After a winter of on-off-on tinkering, I had started testing the 3 separate computers with frustratingly slow progress when moaning to a friend. He said, all matter-of-fact, "sounds like a vacuum leak" and I laughed at him. A week later, I ordered up the line for $10 from the 3rd carb to the fuel pressure regulator, installed it today. I turned the key just to confirm it didn't work and the bike roared to life and purred like a whiny little kitty.
Problem solved, $10 vacuum line. :imwithstupid: