I have the exact same problem with a Saito 80. I got to the point of taking it out of the plane and spent a half day on a test stand.
Talk about pulling your hair out...[:@]

I can get it to run if it's sloppy rich but then I don't have the power. If I tune to peak the mid is fine but full, she drops rpm and dies, and is HOT.

I was told there may be an air leak and it's leaning out.

At this point may fix was to replace the 80 with an 82 while I'm waiting for rebuild parts to arrive. []

Good luck and I'll be watching this thread.

Bob