[Gaz64]

I've been a mechanic for 33 years, I don't have an "engine builder" since I do all my own.

I never said it was right or wrong either, I gave my opinion of what it could be in post 16, then you chime in at post 24 with "your info" which would make no difference to the carb idle speed.

I have never seen this done to ANY carb, it makes absolutely no sense to drill holes in the barrel after the venturi to allow unfiltered air into the engine.
To me it wouldn't make a scrap of difference to how the engine runs from idle to high rpm.

As another member has stated, atmospheric pressure would be on both sides or very near to it.