The bog or stumble is probably caused from a "accelerator pump"malfuntion. The squirter or it's fuel passage could be stopped up;the pump diaphram bad;the pump linkage improperly adjusted.The idle adjustment screw is controling the amount of fuel delivered at idle- not the air--so make sure the idle speed is correct.The faster it idles the more fuel required so 3-4 turns may not be a problem on some motors. A performance cam may require further mods of the idle circut.Paul
