Idle speed screw is under carbs and exactly in the middle of the two pairs. You get your hand under where the hot parts can get you real good.
CV carbs (if it has them) do NOT like more jet, and why so many screw up yanking the airbox to do four. When you jet richer the slides drop and they have already dropped some from yanking the box. Bad way to go. The carbs all open faster and higher when they share common vacuum and why the box is there.
Pick up a physics book kids.........a carb only feeds fuel for 25% of the time the engine is rotating, or 180ish of 720 degrees in a complete single cycle. It is then down inactive and the vacuum in it drops like a rock. if you share the vacuum from the other three though, one of which is always sucking, then the ones sitting dead do not lose nearly so much vacuum effect, ergo, the slides lift higher and faster. Pods allow the off line carb to die like a dog.
Ain't no magic there, just solid engineering principles in action.