I was going to suggest richen up the idle up a hair.
Most times when a throttle snaps shut the engine goes very rich followed by very lean. often the recovery with an idle that is too lean causes this sort of issue.
This is actually the purpose of the dashpot. When engine is set at the lean limit for idle with a load, this helps relax the closing point so the idle well has a chance to recover before throttle is fully closed.
Especially important when autos and A/c etc as a tuner sets the idle at "perfect" no load... lets sat 12.5:1, but when put in gear idle drifts to 14:1, a/c kicks on and engine wants to stall.
I have never actually had a newly bought dashpot work well, seems like they are all too stiff and it always hangs the idle open too much.
Original dashpots seem to work great.