Now I don't know about the Rochester carb you have, but on a Holley 4 bbl, if you get a hesitation off idle, it is because the squirter size is either not adequate or the cam which actuates the accelerator pump does not have an aggressive-enough ramp.
Basically, to make a long story short, it sounds to me like you are not getting enough of a fuel shot when you first stab the throttle. You might want to look at the accelerator pump circuit of your carb.
