The one thing to check engine off full throttle , if things are to far off metering rod can go to high and come out of jet. If that should happen carb will not return to curb idle.

There is a gap, room for movement between the rich and lean piston stops, the step-up spring handles this. It is a tuneable part,modern day eledbrock springs will work.

That white 0.010 shim, if that was in place during adjustment ,that extra gap would allow the vaccum piston,under high vaccum to pull rods down an extra .010 Leaner.