[Gaz64]

Tom,

Adding a hole as in your pic becomes a new "1st hole" not a "4th hole".

The "3rd progression hole" added to IDAs (which only have 2 progression holes) is exposed last, hence "3rd hole".

With your triples, what size plumbing are you using for intercylinder balancing?

If each intake runner is connected together to gather vacuum for power brakes with hose too large, then each cylinder will breath through more than one barrel and the butterflies will be virtually shut to get a normal idle speed.
Ideally you want the first progression hole ready to be exposed as soon as the throttle comes off idle.

What speed does your engine run at, at this point in the throttle?