Ok. This is turning into a dog turd, the more I mess with it the messier it’s getting.
This is what I’ve tried so far:
Disconnected vacuum pod and plugged port. Drove it and got it to stumble, though seemingly not as bad.
Retarded timing all the way back to 10 initial which made my mechanical top out around 24. This lowered the idle rpm a lot so I turned the idle mix screws to get best idle. Idle vacuum was now down to 6ish from a previous 10-11. Tested. Stumble was still there but seemed to occur at a lower rpm.
Returned home and went back to previous settings. Tested. Runs better all through the throttle range except for this damn stumble.
Current setup:
24 initial, 34 total with can unplugged.
Idle rpm 800 with 10-10.5” vacuum.
37 primary shooter, 31 secondary.
T slot is unmeasured after doing all this fiddling but pretty sure it’s in the ballpark because the idle mix screws are very responsive and with that much initial timing I had to turn the idle screw way out.
I don’t know where the hell to go from here.... try a small wire in the IABs?
I will map my timing curve tonight, still suspect it’s too fast.