Baseline the carb to stock specs and it should be close, within 5 jet sizes of optimal. Only so much air can flow through the venturis, with appropriate fuel to match. Soulnds like you have the typical Holley problem, too rich at idle. For some reason they make their idle feed restrictors too large by nature. This makes it so that they run rich and stinky. Even with the mixture screws in only 1/2 turn out it's still too much. I've worked over a few holleys and it's been a lot of trial and error.
Devin
