Ok, As Bee71 stated hot air compensator normally for AC cars and auto, but the 70-71 hemi cars had it regardless. I have seen articles state if can reduce airflow 25cfm, but I think that is the version shaped like a T vice some like hemi which are just straight.

Removing it and you can put inverted expansion plug or piece of aluminum rod in hole.

AVS also have off idle valve which is what I thought you were talking about. It is a check ball under cap in the top. Off idle as manifold vacuum is exposed to the metering circuit it opens the ball and draws extra air to lean off idle mixture for exhaust emission control. I have seen rebuilt AVS where this gets plugged or been capped.