A little clarification on adjusting idle air mixture on eddy carb

I guess my main concern with using a vacuum gauge is you cant do one mixture screw at a time right? You have to do them both back and forth until peak vacuum is achieved?
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You have to go back and forth a few times regardless of RPM or vacuum. This in part is because most intake manifolds have some sort of balance / feed through between the two sides. Of course an open plenum/ single plane manifold is moreso