Carter BBS Slant 170cui idle problems

Above that white spot is a threaded entry port for heated air from the exhaust manifold, travels around. Half moon shape, at the left of the white. There should be an entry point into the Airstream of the carburetor. It's almost visible that little black spot. It's possible that there was a restriction bushing in that hole at one time. That fell out a long time ago, possible vacuum leak