If you lag is 1/2-3/4 throttle, it is carb related. As previously mentioned, vacuum advance is light throttle only. For now I would cap the vacuum advance at the carb (no need to cap at dist) and set the timing just below the point where you start to get ping using the gas you typically run. This will have your ignition in a stable condition so you can focus on the carb.
The Owners Manual that came with you carb has some pretty good tuning advice. Read and heed. First make sure your float levels are correct. Then, if the jetting is basically close it may be as simple as going 1/4 turn tighter on the secondary air door.
Then, once the base timing and carb are where you want them, you can connect the vacuum advance and set it up. (Timed port is on the passenger side of the carb).