[ducatiman]

Part of the pilot circuit...the 4 little holes are known as "transition ports".

I'll surmise the hole is designed to provide production access allowing drilling of those ports from the exterior of the venturi, then permanently plugged afterwards, to be left intact from that point forward.

I've never had to remove or replace one before, but accurately measuring both diameter and depth in order to source some sort of replacement should be doable.

A small plug possibly from radio control car, automotive, electronics or firearms industry....you'll need to do some homework.

Do NOT use any sort of liquid sealant as the port beneath must remain.

The intended target fuel mixture screw lives under the EPA anti tamper plug shown at 12:00 from the brass plug.