AFV is applied in open loop operation only, whereas EGO correction is applied in closed loop only.
AFV is also the reason, snake oil like the mentioned devices will not work. Fuel is added because of a fake temperature signal, EGO corr. removes fuel in CL to get a stoich mixture, AFV is dropping because of EGO, fuel is removed in OL, and you are where you were before. This is also the case for each ECU manufactured the last 15, maybe even 20, years. Better donate for a copy of EcmSpy, because this is known to work.
Stumble at very low engine speeds seems almost always a timing problem, and take into account that all "Idle ..." settings get active once engine speed is below the Idle Max. Engine Speed.