Check all possible sources for vacuum leak(s), not just the carburetor. With the engine idling, try spraying something like WD-40 or carburetor cleaner around where the manifolds bolt to the engine as well as the bottom of the carburetor and EGR adaptor. If the idle speed changes, you have found a leak.

Check the vacuum hose going to the brake booster. Listen when applying the brakes for a hiss. Sometimes the booster diaphram leaks.

Check the PCV valve and its hose.

Check any and all vacuum hoses and make sure that one or more of the rubber caps on the manifold vacuum trees as well as on the firewall have not cracked or fallen off [this is not uncommon!].