Stumble issue

Bend the accelerator pump rod so that only 13/32" of the acelerator pump shaft is sticking above the carb body and I bet your issue disappears. The Edelbrock pump is typically so high in the body that it is above the transfer slot. When you tip in it just pushes fuel back into the float bowl and not top the accelerator pump squiirters. That little trick has cures 99% of the off idle stumbles I've ever seen in the AFB carbs.Also check Fugly racing afb write up