Try running it again and see what the hand unit says at the exact second it cuts, look at the rpm and see if it drops a split second before the it stops. If it does then its the rpm sensor. Another way to test it is to plug the hand unit in and spin the engine over and watch the rpm reads right down to 200 if the final reading is much higher, say 800 or so then theres sensor problem . I had the exact same problem on someone elses engine the other day, flamed out at the same rpm as you and the rpm only read down to 900 but once I got a strong magnet and rubbed it round the inlet it sorted it out straight away ( a tip I got from that guy who did the RAM ecu's) , read down to 200 rpm and ran perfect.

try it it might just work!
jason