[WardL]

I believe the atmospheric pressure is 14.7 PSI outside the air cleaner. As the air gets sucked into the carb, there is slight pressure drop depending on the air cleaner as the air travels down the venturi. At idle, the pressure just above the butterfly would be pretty much 14.7 and very little flow would come into the carb from these little side holes. At full throttle with the butterfly wide open, the pressure "upstream" of the butterfly would be at the lowest pressure, causing the most flow of air through these little pin holes into the engine. To me, the Holley Tech answer sounded more like they didn't really have a good answer so they came up with a flimsy response. Maybe it was an "improvement" Holley later decided wasn't such a good idea. I say plug the holes if only to prevent dirty air from getting into your engine. Any benefit the holes offer can't be worth the extra dirt in your engine. Pretty interesting little issue!