Well, a couple weeks back I took the Vette toa friend's house and we reprogrammed the computer for larger injectors. Turns out my problem wasn't an injector issue at all (though I still kinda needed larger injectors) but coil packs 2 and 4 not firing.
It's not the packs, the plugs or the harness on the coil pack bracket. All of these were exchaged for new ones from a working car and the problem was the same.
I tested the continuty of the inignition control signal lead from the pcm to the connector for the coil packs. It's fine. I'm a little mystified. . .
Here's the diagram. Any idea on what to check next. I suck (extra) at electrical. I suppose it could be the wires, now that I think about it, but I find that remarkably unlikely since they are essentially new and worked fine before. [Click on the pic for larger version.]