annular vs downleg

Velocity can be slowed due to a larger manifold runner if the cylinder volume
isn't proportionally increased by means of bore and or stroke.
As an attempt to make up for this slower column or weaker signal at the base of the carb the booster can be swapped for a more sensitive design. This design is the annular booster.
The carb can remain responsive with less velocity being pulled thru the venturi.
Increasing the volumetric efficiency if the correct balance of fuel and air is met.
I have never used annular boosters myself as I haven't strayed away from stock
stroke or excessively oversized ports.
Perhaps you can get some here who have needed them to chime in with a better
description or experience.
I have always wanted to try them on a tunnel ram but never actually felt it was necessary.
All my engines seemed to do good without them.