Vacuum advance can't really be adjusted unless of course you've got an adjustable vacuum advance canister. Sounds like your lookin' to set the mixture on your carb. A vacuum gauge definitely helps. You'll want to connect it to a full manifold vacuum port, preferably near the base of your carb. And yeah, shoot for the highest steady vacuum and then back screw in (lean) about an 1/8 to 1/4 turn. The idea is to get as lean a mixture as possible without affecting performance. And you'll want to do this with a warm engine and it's preferable to do this after setting your distributor timing. Also, leave your air cleaner on carb as you make your adjustments to mixture and idle.
