I remember playing with this a lot a while back and ended up just accepting that the injectors flow too much per min pulse for very low driving conditions. With the RoadRunner PCM I played with offset, min pulse and adjust tables etc. You basically can get to the point where you command such a small pulse width that the injector cannot open, flow fuel and close and you get an AFR like you are in DFCO.

I'd be real interested in other peoples findings though