I had a brainwave that maybe the problem was with the gas, since I had pulse on injectors and spark. So I drained a bit over a gallon out of the tank via the pump access a PO "installed." Turned off injectors, and did a much more liberal application of starter fluid, aiming to get toward the back passages. It just about turned over a couple of times, but didn't want to with the injectors hooked back up.

So the plan now is to try and drain more gas out of the supply line, and at the same time take the injectors off and see how they are flowing. I'll be asking around locally if anyone cleans them. Cable arrives today to look at any codes. We're almost there, maybe.