Vehicle stalls while driving

5.4L (Eddie Bauer) will stall while driving 70mph on the highway. I can wait 2-10min and try the key again and it will run fine after that. This can happen once every 2-3months or at rare times 2x in one day. This can also happen while driving slowly through an intersection. Climate not an issue as it will happen in cold or hot weather. When it starts to stall it will futter a little. Feathering the gas pedal does not make a difference. I've taken it to a reputable FORD dealer and a good local one in town and they cannot find anything. Response - bring it back when it's not working. There are no error codes when this happens so it can't be tracked. I can hear the fuel pump engage when I first put the key in so I know it's getting the pressue it needs. I've replaced the alternator harness thinking there could have been a short which showed a wire burned, but the problem still exists. I've been told the IAC, TPS, coil packs and spark plugs could be causing the problem. To me it doesn't explain the sudden shotdown of the entire system when driving 70mph down the highway.