Must say that RCKen gives excellent answers. The post with the pictures is superbly complete and detailed.

But . .

I have been using air bleed carbs since 1966. Currently own 6 engines with them. Currently flying four of those.
In the past 10 years, I have acquired four engines with the "better" carbs. They work great, too. I believe RCKen is infering that these can be tuned more finely. If that belief is true, Ken is absolutely correct again. If I'm wrong, he is propably still right.

Dr1Driver's post gives you the info to tune an air bleed carb. Not much of it needed to achieve the purpose for which the thing is made. I have never drilled the hole.

If you are wanting precision tuning, get an engine with true low speed needle. Most will also have ball bearings, higher compression and much more power.

As you did not say what plane you are using, I will not suggest the proper propeller. That will also make a difference in tuning these carbs.

Ken, AMA 19352