What is this part of my carburetor? And what is the function

I have removed the carburetor of my car for repair . Its a Aisan 14120 carburetor. My car is a 1987 Toyota Tercel 4wd 1452cc 2bl manual driven car.

I know the functions off all the components instead of this shown circled in the following picture.

It is a two barrel carb. That part has a one orifice for the secondary barrel throat. Inside this small chamber, there is a plate like Valve. Other end goes to the intake manifold.

I added some more pictures. It lies in the direction of the arrow in top view.

Can tell me What is this part and what is the function of it?

do you see the part in this diagram?

Yes. but this part is not mentioned in this diagram. It lies in here.

After Googling for long period, I found this as a place for Thermostatic valve. Unfortunately that thermostatic valve has been removed by the previous user and added a valve like plate.

Now that valve production is discontinued. So will never able to use this part.

you could check to see if you can find a carb at a junk yard or on ebay or something