I know its late, and I'm not (or ever was) expert, but the open-loop control jumps out to me on this.

I am now big on being very sure about vacuum leaks (because of age), but this is not how it reacts when it is vacuum. Two vacuum spots you may have missed - the tee beneath the S/C snorkel and the Evap solenoid near the EGR valve (it has an O-ring inside).