I have a TST box on my truck and today I was driving with it set on 4pw and 4 trq. And I got on it a little to pass a car and the truck started cutting out at aprox 2500 rpm's... It will do it in Drive or Over Drive even on setting 1 it will do it. If I turn the box off its drives normal with no problems. I have no Codes and no Limp mode on the trans... I am guessing it’s the Box. Anyone else had this problem. I have had the box for about 2 months now and it’s never skipped a beat. nor has the truck.

Later today I tried to get it to cut out again and its seems to be working fine now??? :confused:

I've only noticed this when my high idle switch was left on. Since yours is an 03 and came with the high idle already its probably not the culprit. :confused:
Blake