I have a varity of glow engines both 4 strokes and 2 strokes, ranging in size from 0.15 to 1.20. I have Saitos, SuperTigre's and OS's. They all idle better and have better throttle up at lower nitro contents. Clearly peak power goes down with the nitro content, but the idle and throttle response is better, partucularly with my .40 size motors which will happily idle on 5% without loading up while the idle goes rough after a couple minutes at 20% nitro. I would have thought that higher nitro would have a better idle, not the other way around.

At the other end of the stick, my .80 and .91 Saitos are happiest at full throttle at about 10% nitro. Depending on temp and air pressure, both my Saito's have been known to backfire in flight on 15% or higher, and yes, having the valves adjusted right makes a big differnce, but does not cure the problem entirely. All my two strokes range from running better and better at full throttle on higher nitro (especially the small ones) to at least not displaying any bad habits (the big ones).

Back to this idling issue, properly tuned, the correct needle setting is always leaner with less nitro and ritcher with more, (and yes I' setting the low side as well so that's not the cause), but since the revs are higher with more nitro I would tend to think the engines are running at about the same stocastic mixture if properly tuned, regardless of the nitro content

Do I just have a couple of engines with unusual characterisitcs? Are engines just running cooler at lower nitro levels and therfore idling better? Is the brief "lean surge" as one opens the throttle less prounced with less "powerful" fuels? Is it a combo of these factors?