<VV> Corvair stumbling

[Gary Swiatowy]

My 65 Monza 110 automatic, has a weird problem.
Starts, runs, drives well when its cold. In fact, when cold it runs perfect!
But after running for 15-20 minutes or so, when I come to a stop, it wants 
to stall and stumbles, spark knocks, and has no acceleration.
After it fights its way back up to speed again............its fine.
This problem has plagued me for years but was especially bad yesterday on 
the way back from a show.
I've become so disgusted with this over the years, I litterally park it and 
drive a different vair..........
The chokes do open, and are not falling closed.
I have swapped on different carbs.
New points and condenser.
tried a different used coil.
New fuel pump

Could the distributor itself be bad?
Could the plug wires be shorting when warm?
(no arcing in the dark) and the wires may be 6-7 years old but no more than 
2000 miles on them.

Ideas?

Gary Swiatowy