Well, I get what you're saying, but the fact that the P13 is OBD-I would seem to have nothing to do with his issue because he was using the P14, which is also OBD-I. I don't think his problem is there (although the fact that he was running the P14 is scary enough, but I guess the VAFC is taking care of the air/fuel ratio)... Anyway, it doesn't seem like the firing order would be an issue because he never should have had to touch any of that whilst swapping ECUs.

It sounds more and more like an ECU issue, because the P28 ran well without having to bypass the VAFC. It's really hard to diagnose things like this when you don't know everything though, like who did the swap, programming, wiring, etc. Good luck if y'all meet up this weekend, though. Hope you get it sorted out