I mean when it’s hooked to ported vacuum, or “timed vacuum” as it’s called on the diagram. It’s the port that gets the same Venturi as the jets I believe? Manifold vacuum decreases under load but Venturi “vacuum” increases does it not?
No. Not under load. Under no load or part throttle it's there, but it's still controlled by the throttle opening. There's only 1 vacuum source and it all drops off under load.