Check out this thread and print out the PDF file for referencing when you're out with the car.
https://www.rcnitrotalk.com/forum/threads/nitro-tuning-tips-and-tuning-flow-chart.60832/
If it isn't a clutch problem, as @mrbones suggests, it could be that your HSN is rich but your LSN is lean. The LSN controls the idle and takeoff and the HSN is the WOT. Too lean on the LSN will also cause it to run too hot even if it's just idling.