If you have your old injectors you could try putting them back in and see if the problem goes away. I would get on the phone with II and tell them whats goin on.

I do have the old injectors. I'm gonna do the "air in fuel test" and a few other things before I tear into it.

Well you can try that but, you said you have a steady fuel press. reading. Have you noticed any change in noise of the lift pump ?

AirDog sounds fine. As far as FP, it's steady but that doesn't mean there isn't air in there according to Blue Chip diagnostics page. Couldn't hurt to check. Also, Dock said he fixed a similar problem with a Draw Straw.