17 Idle mixture adjustment is performed at the primary throttle bores. Once the engine has stabilized at idle, each side needs adjustment. If you’re using a manifold vacuum gauge, you want the most vacuum possible at idle speed, which should be around 600-800 rpm. Vacuum should be 17-22 inches at idle speed. You want the carburetor at curb idle with a tweak of transfer slot visible with primary plates closed. Throttle position should be at idle, not fast idle on the choke circuit.