Accelerator Dump out.

[Ericgileza]

I am having a problem, wonder if anyone can give some prospective... First (its a 1971 K10 4x4, all original, 307 2bbl, m20 3spd trans, np205. It ran junky before i did anything to it, but it accelerated when hitting the pedal. I rebuilt the orig 2bbl carb, runs, I'll say less rough, but hit the pedal, and it dumps out. If i pull off the accelerator quick enough it bogs out but catches it, itself, and re-idles but rough. Then if i press down the pedal slowly, it will climb, and at release it will purr???ANY CLUE thx for anything