If the idle screw is turned all the way in (like bottomed out and spring bound up), then you have essentially bypassed the straight section of the needle, the slide is well and truly open, and the pilot and air screw are getting towards the end of their effect. Thats why adjusting the air screw isn't doing much. Its also why you get inconsistant idles.
Set the squish to improve consistancy and effeciency. Best mod for any 2T.
Set the carb so that the slide is only open, get a needle, and cycle through pilots until you find one that allows the bike to start and idle with the air screw at 1.5 turns out. Remember a cold engine thats well jetted will start on the choke and not off. Thats why its there. If you can take the choke off too soon its too rich. If its cold blooded and won't come up to temp eaily and bogs a lot its too lean.
Slide cutaway, pilot jet, needle diameter - 3 pieces of the puzzle that all need to work in harmony. In my opinion it sounds like your needle/slide is too rich so you have gone with a small pilot to try and crisp up the 1/8th throttle, which has given you some bog and a smaller pilot than you'd expect. You've also had to lift the slide (idle screw) to try and lean the bike out to compensate as well.
Without knowing the model or the slide its documented that #7 works well. If thats what you have then the magic will be in the needle.
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