Hyper 21 problem

[Defcon]

So, just recently put a hyper 21 into my hotbodies lightning 2.
It's generally running fine, but once warmed up, seems to want to quit after WOT.
After slowing or breaking, the engine idles very low and begins to die untill you blip the throttle. Normal idle is then restored.
This is only after WOT.

Also I've noticed occssionay there's a sucking kind if sound after shutting off the engine, as if air is being drawn through the fuel line or filter maybe
Is that normal, not noticed on any other nitro engines I've used.

Thanks