It shut off when? Accelerating or comming down from a highspeed run? If it was coming down from a high speed run or during the highspeed run, the HSN may be too lean. Good sign of this is loss of power is gurggling or engine stuttering at high speed.
Could be your glow plug..maybe running too lean. Sometimes the ezstart will show glow plug fine and it really is burned out, check it with an igniter to be sure and if it is the plug, richen up the high speed needle abit.