[keitho64]

I know some of this may be repetive but here are my thoughts, in no real order:

Float level / needle valve - make sure the needle valve is not allowing fuel to bleed past and that the float level is right.

throttle linkage - make sure it is adjusted - disconnect all linkage and see if it will idle steady - if so verify the linkage

Advance weights - make sure the advance weights are not rusted / binding and that the springs are not weak. (I had this issue on my Marelli - car would idle first and as soon as you bllip the throttle it would never idle back down. I took the weights out, cleaned them and installed new springs)

vacuum leak - besides the usual places check around the throttle shafts

I would suspect the dizzy advance or something in the linkage hanging up.