Hole in holley 1920 carb?

I can't view your photos at work.
I posted years ago about the ~4th Holley 1920 I tried over many decades that finally made my 225 idle like a kitten. All the others gave a rough, missing idle (lean?), even thru various mechanical changes, including finally a complete rebuilt long block. The carb that worked had a hole drilled in the throat. Seemed strange, but I stuffed a cut Q-tip w/ plastic shaft in so that air got filtered.