Vacuum Leak?

Installed 4 seconds flat ignition and distributor this weekend which works great but didn't solve my engine shake in idle. I have discovered once I hook the the vacuum advance to the distributor in idle condition this is when it occurs? If I put my hand partial over the primary on the carb, idle increases about 400 rpm and the engines smooths out. If I hook up a vacuum gage while idling at 800rpm before putting my hand over the carb, vacuum bounces from 8 to 10 because of the irregular idle. I do not want to pull the intake manifold. It has a rebuild AVS by the prior owner. Could this problem be in the carb?