If you want to check for vacuum leaks SAFELY, first is after it is warmed up slowly block off the airhorn with your hand. If it wants to idle faster, you have a leak. Second, take a spray bottle filled with WATER, not any flammable liquid. The whole point with this is to get a change in rpm. Start at the base plate and slowly work your way around the base and then move to the throttle blade/linkage area. If you have a leak, the rpm will drop. Also check the PCV by blocking the open end with your finger. If you have power brakes, check the valve/hose at the Booster. Both open and blocked off. This should keep you busy. Is it a problem idling in gear ? Does it diesel when you shut it off after running a while ? Do you know the proper way to adjust the idle air/fuel screws ?
how to adjust the idle on a holley carburetor - Bing video