yes, drop the vacuum advance for tuning.
find what the engine like at an idle, and then find what it likes wide open. adjust accordingly..
also, does this have an MSD box on it by chance?
have you took a visual inspection in the carb, looking at the boosters at an idle to see if it's clean or dirty (droplets of fuel) coming out of the boosters?
do the rpms every change greatly or erratically when trying to adjust idle either by the mixture screws or idle speed screw?