Just to clarify a little bit: there are generally 2 types of ignition timing advance. First is centrifugal or mechanical. Its purpose is to increase the amount of timing advance as engine speed increases. Then there is vacuum advance. Its only purpose is to increase timing advance slightly under part-throttle conditions in order to increase gas mileage.
In most cases, you can disconnect the vacuum advance completely and still have a good-running motor...as long as you plug the vacuum line and don't induce a vacuum leak.
In my experience, a throttle bog comes from running too lean...whether it's because of a carb mixture problem, a malfunctioning accelerator pump or a vacuum leak.
Vacuum advance is normally not the cause of a throttle bog.
