IDF idle jet size impact on AF ratio

[grrrdot]

Hi,
I'm getting my 40 IDFs all dialed so I went for a drive today and logged the AF ratio.
I'm at ~12.1 at idle with the idle stop screw 1/4 turn in. As I slowly accelerate the AF ratio quickly leans getting into the 14s occasionally getting to 15, by the transition its popping out the carbs. Once I get into the mains the ratio is OK again, around 12.x at WOT.

Does anyone know how much the AF ratio will change with one jet size change?
e.g. if I went from 55 idles to 57s what change should I expect in the AF ratio?

-G