I'll say it again - you should go to a shop that has a quality emissions analyzer and get your idle CO measured. Adjust the ECU knob and verify to yourself that CW does make it richer and CCW is leaner. See if you're WAY off of where you should be - for example, "really lean" is 1% or less, and "really rich" is 5% or greater.
Don't expect D-Jet to ever have the idle stability that a modern EFI system has. Most modern engine management systems have an idle stabilizer device that dynamically adjusts the air bypass to maintain a rock-steady idle. D-Jet is for the most part an open-loop system without feedback (if you neglect the speed control signal from the trigger contact points, which isn't used in a feedback manner,
AFAIK).
Common idle stability problems are that when the car gets hot, idle tends to bog, and when you switch on heavy electrical loads (e.g. lights + heater blower), it bogs. The goal here is to set the idle to the best compromise setting (assuming you've first assured yourself you have everything set to spec: mechanical, ignition, timing - FIRST!). I go out, run the car hard, then come stop, switch the lights on, and set the idle to the lowest RPM I can tolerate (about 800 rpm or so). You'll find that if you do this, your lightly loaded (warmed-up) idle may be as high as 1200 rpm. That's about as good as I've been able to get it.