@Mattax was saying something similar to what @crackedback said above. Most new billet blocks come with a 4-5 hole replaceable emulsion stack. It’s very tunable and you can quickly get carried away chasing a tune up. For almost everything we (300-600hp basic street strip stuff) do a simple 2 hole stack like the original Holley blocks have generates a fairly consistent fuel curve if the MAB and IAB are in range.