Too lean is my vote too. Get an extra set of hands and hold the plane straight up (full power), then set the needle just short (300 to 500 rpm by ear) of peak rpm. When you put the plane back on the ground the rpm should drop slightly. Then you can try the pinch test. If the rpm increases slightly when you pinch the fuel line, then you are ready to go.

If it still cuts out in flight, then your problem is elsewhere.

Please do not cut off any body parts doing this...