Howdy:
You might suggest that he do a google search for Autolite 2100. There is lots of good info on the web. Annular discharge booster is the little donut like ring that hangs above the venturi, or the narrow part of the carb throat. The annular booster has outlet holes all around the inside of the donut. Other carbs have a singular hole in the booster. The many smaller holes ingest a finer spray of gas into the air stream, causing the gas to vaporize more quickly as it enters the intake. Annular discharge boosters can show an improvement in idle and off idle acceleration.
The 2100s can use a Holley power valve to fine tune WOT air/fuel ratio on acceleration.
Autolite 2100s are lighter that Holley 2300s and most Carter and Rochester 2 barrel carbs. They are the easiest carb, ever, to rebuild. The 2100s have no bowl gasket lines below the level of the fuel. They are better bowl vented than most carbs.
But the trade off is that they cannot be fine tuned, internally, as easily as a Holley 2300. Main jets are harder to come by where as Holley parts are available at most part stores.
One tip I saw at a truggy (truck+buggy) rally was adding a rubber hose loop from one bowl air vent to the other. The top of the loop had many holes in it. The idea is that if you have your fuel level set fairly high, and are on extreme off angles fuel will not slosh out the bowl vents.
Hope that helps.
Adios, David