I had a similar erratic, jerky low power event on my 2006 E350 6.0 diesel SMB a few years ago. After driving several thousand miles from California through Canada up the Alcan highway, the jerky, low power event happened just after topping off the diesel tank near the U.S. Boarder. It was especially noticeable when first starting up in the morning and trying to climb even a moderate hill. I thought that I must have gotten some bad diesel fuel from the "podunk" station where I was trying to use up the last of our Canadian cash,.. We limped several hundred miles home to the Kenai Peninsula, Alaska. The local Ford dealership service was able to quickly determine that there was a rubbed wire in the engine top wiring harness (they had seen this one before) and quickly eliminated the problem with a new harness.
'06 Ford 6.0 PSD E350 4x4 RB50 Customized SMB w/penthouse, Aluminess Bumpers & roof playpen. All Diesel & Electric: Espar Hydronic Heat, Wallas Catalytic Hot Plate Stove, VitriFrigo 12v Fridge, Dieselsite & Amsoil Filtration,.. and my other RV is a BMW R1200GS.