Having a problem with a customers 08 5500. History on truck - 248k and just bought it from someone on ebay. Ran perfect when he got it. Has DPF delete with boxes plugged into sensor wiring. Recently he got a lot of water in his fuel, like 20 gal of water and only maybe 5 gal of fuel from a cracked sending unit. We cleaned tank out completely and replaced fuel filter and added fuel tank antigel. Filled tank with fresh fuel.
Now for the problem - at approximatly 2000 rpm if you hold the throttle there, the vehicle will start to load up (smokes a raw fuel smoke like a decompressed motor) and rattle like a fuel knock real bad. If you let off the throttle just slightly it will go away or if you get on it harder it will go away. Only code we got on the vehicle was for the filter for crankcase needed replaced.
PLEASE HELP ME!!! I dont want to just throw parts at it. All parameters on sensors are where they should be when running. Where should I start???

 

He should be contacting the station where he got the water in his fuel to document the case.

Water in fuel on these Cp3's could cause all kinds of problems and thousands of dollars in repairs.

I know that doesn't help repair the truck but you could be looking at chasing this for a long time.

 

The water trashed one or more injector. I would have all six checked.