weird cutting out problem

My money is on the coil, my ramcharger set for a while and my older son needed to use it and as soon as it got up to temp he thought it ran out of gas and parked it and called me, I had my wife drive me to the truck and it fired right up and as I was getting close to home (about 8 miles) it started stumbling, but I made it home and shut it off.. then tryed to start it!! no start! I put a good ecu on still nothing.. I put a used coil on and it fired right up, that coil is still on it and I have had no problems in a year.. Just a thought, like some one said here when the coil warmed up it would not do it's job, but when it was cold it did start and do fine.. hope this helps and you get this problem behind you soon.