Hi Adam---------------The vacuum advance is the round "canister" that is attached to the side of the distributor. It should have a small diameter hose connecting it to the intake manifold.The vacuum advance is important when under partial throttle, after the first stages of acceleration the counter weights on the bottom of the distributor shaft take over and advance the timing the rest of the way. It's primarily for better performance and fuel mileage at lower engine revs. If your car is running well now, don't worry about it. There are many cars with triple carb setups that don't use the vacuum advance at all. FWIW
Roadman