DIY Idle-eze?

Dellorto carbs have that per bore to balance flow. Also done on later model Solex 34 used on VW.

I use a pwm controlled air valve on my efi systems to control idle speed, the system also adds fuel with air.
Most carb with idle air screw, keep throttle only 1 fine thread turn from closed, so throttle blade does not contact bore. Bypass air is much better controlled for small amounts, vs throttle stop adjustment, that is very non linear as throttle opens.