It is like a chain saw, idle and WOT. Could just be the carb. I have an XYZ 20 but have not run it yet to compare. It has a Walbro carb, the DLE has whatever it came with, but not a Walbro. There is no linear to it, once the throttle plate gets to half open, it is pretty much running at full speed, there is very little increase in RPM after that. Top end is between 8600 and 9200, which is where it is supposed to be. On the 4 *, doesnt really matter much, I fly it WOT most of the time anyway, only when landing do I have it at idle, or when I am practicing low level passes is it below half throttle.