Put a vacuum gauge on it. You might have many places to check and need to isolate them one at a time. I had a vacuum line crack at the grommet in the firewall. Could not see it but when I pulled it off and plugged that line off the problem went away. Start with the basics. Are the bolts on the manifold tight? The nuts on the carb base snug? Are all vacuum lines good and snug? Is there a leak at the vacuum advance? At the place where the vacuum advance goes in to the carb? And that is just off the top of my head. Put a gauge on it and fix them 1 at a time. You will get it. Then go to other issues. Yes it will run at idle with out the vacuum advance hooked up.
