I'm running this box in my Demon. I had this issue with engine cutting out at 5700 too. Then the dyno operator said it sounded like was hitting the rev limiter, though it was set to 6200. So I set it to 8000, the motor reved to 6500 clean as could be. So now I set my rev limit at 7000. I'm running the 508 Mopar cam. I gap my plugs at .050. Set your limiter up higher and make a pass to check. The 508 cam pulls hard to 6500, but I shift car at 5800.