I am of the opinion that the emulsion tubes, and accelerator pump jets with their various diameters, holes sizes and patterns are intended to remidy the very condition you are describing. There is more than one Main jet/air corrector pattern that will get an engine running properly. For instance a Roller cam engine because of faster valve timing and action can generally utilize a smaller main jet than a flat tappet engine, because the roller cam engine creates a stronger signal (depression/vacuum) sooner that acts upon the fuel within the main well. In the idle system the 3rd hole receives a signal "later" with progresive opening of the throttle blade, the notch in it passing the hole after the OEM hole is exposed. Then fuel is drawn from it rather than the other because of a stronger signal that it is receiving. Then when the blade is open far enough, the siganal becomes strong enough to pull fuel and air from the auxillary venturi. However, once the 3rd hole is drilled It may work for one application or cam in a particular engine but not another?? Just my opinion, not in favor of drilling holes. The volume of fuel mixture rendered is determined by how far the mixture screw is opened combined with the accelerator pump shot.
Here is a link to a great article of how to completely rebuild the 48 IDA, included are several pictures including one of the aformentioned 3rd hole:
http://www.aircooled.net/gnrlsite/re...idarebuild.htm