Diesel Doctor

Today while backing our 5th wheel into the driveway, the truck kept dying on me. I finally got the trailer parked and immediately changed the CPS thinking that was the culprit. But the truck continues to die when it is under a load and only seems to be doing it in reverse I can duplicate the problem by standing on the brake, putting the transmission in reverse and when I hit 15-1800 RPM, the engine just dies out. It will start right up again and run fine. There are no codes being thrown so at this point I am looking for any suggestions as to what the problem might be. This is a 2002 FORD F-250 7.3L Power Stroke with Auto transmission. Thanks in advance.
Jack