Help asap truck shutting off while driving!!!!!

I have Duramax LB7 2003 Chevy; I have only had this truck since December and have more problems then its worth.
I have replaced the injectors because I started having gas in my oil. Recently it started SHUTTING OFF WHILE DRIVING ON THE HIGHWAY. You will be able to drive it up or a hour or so and it will shut off and not come back on till it rest then will start back up and will continue to the same thing again after driving it so long. I have noticed that as long as you don't slow down and keep your speed up it will run and not shut off. I have took it several places like a GMC dealership that told me I needed a new motor because the crank was moving... it wasn't. I have replaced the crank sensor also and some parts of the fuel system. Another diesel specializes told me it was either the computer or my programmer. I know nothing about the EFLLIVE program or what to do. I need this truck to be fixed like yesterday as I need for a work trip and its my only ride.

ANY ANSWERS ON ANYTHING WILL BE HELPFUL!!!!!!!!!!!!!![/B]

Try returning the truck to stock. When it shuts off does all the gauges keep working and the engine just dies? Or does it seem like the ecm momentarily restarts? There are some things (atleast on the newer ones, not sure on the LB7) that can cause a shutdown while operating the truck.

Thanks

Mitch