Edelbrock Air/Fuel Screw Not Working!!!

[savatreatabvr]

I have an Edelbrock 1407 on my mid 70's C/20 454. The drivers side mixture screw works but the passenger side doesn't. I can screw it in all the way and nothing! I also hear a high pitched vacuum leak while driving at steady speeds, when I let off the gas it stops until I give it more gas. I've played with the adapter plate (Edelbrock 2696) and countless gaskets with no help. I've sprayed water around the intake manifold and carb and no leak! Could the throttle shaft be lose enough to create such a loud vacuum leak? I've checked everything else, what am I missing?