34PICT-3 CARB Volume and Bypass Screws? Function???

[CapnDavy]

OK, I'm up to speed on the textbook carb adjustment procedure... but I still can't obtain a consistent idle.
The engine idles fast, but when I use the gears to brake the car (lots of air going thru carb with not much fuel) and finally brake to a stop at the intersection the engine quits. I start it up and it goes back into it's "fast" idle configuration.

When I get to adjusting the bypass screw (large one) I can close it down with rpm decreasing until about 800 rpm. Any more and the engine quits. It is not steady and fluctuates quite a bit +/- 50 rpm. To get a smooth idle I must set about 1000 rpm.

The volume screw doesn't seem to have much effect. I can turn it in until the engine quits, the rpm doesn't decrease gradually as I turn, it just quits. Turning it out from the initial 2 1/2 position doesn't seem to increase the rpm any.

Any thoughts? And please comment on the following:
Could you describe the function of the volume and bypass screws? What volume is being adjusted? What is being bypassed? And what is doing the bypassing: fuel, air?

[CapnDavy]

I found that the idle jet (screwed inside the tube on the right hand side of the carb - beneath the screw on cap) was not there! Got a replacement from a basket case carb from Ebay.
Fixed problem.