The problem you're describing is almost always caused by dragging throttle plates, especially on a new carburetor. You made a big mistake going with a Holley- - - - -now about all you can do is make the best of a bad situation. No, a vacuum leak would not respond to tapping the throttle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!