when you say fall on it's face do you mean the boost drops to vacuum. Go outside go WOT in a gear where it won't do that and aburptly let off the gas real quick. Is that the same feeling? If so that's your ECU pulling. If you're on a Stage 0 and you go over 17psi expect to see that fuel cut (it's really a spark cut) at speeds above 75 (basically top of 3rd onward)