...if you have a Holley carb, there are 2 Mixture Screws, one on each side of the Primary 'Block'. After setting these as described, The 'Final' adjustment is made, with the Engine running, adjusting both screws Simultaneously. Turning each in until the Engine Starts to Stumble, then screw back-out for a smooth idle. One will Affect the Other, this is why the 2 must be Adjusted Together. Should You get that far.
I will add, I have found Loose connections at the AMP gauge AND at the Multiple Ground Connections at the Stud, located UNDER the dash at the Drivers' (left) 'A' pillar. Both gave me the same problem of a Mystery Engine 'Stumble', Cut-Out.
Marlin