Exhaust gas pressure during regen.

[MPDiagnostics]

So, first of all, are you saying you pulled the DOC and DPF and "looked at it" and then put it back? Theres not much for you to see other than some of the surface stuff. Just because it "looks clean" doesn't mean that it is clean on the inside. The evidence of the regen history is showing you that.

You didn't state if you even cleaned them out... And if you didn't you STILL need to do that. Do the EGR tuneup like Rawze said. Make sure IMAP, EGR, and Exhaust sensors are fresh and pipes and tubes clean.

Do you get a bunch of smoke at the beginning of a regen? That has an indication of face plugging of the DOC is bad.

We also need more info on the rebuild you did. What kind of cylinder head you put on there - Aftermarket or OEM - or did you reinstall the OLD head? What kind of injectors are on the truck- Aftermarket or new OEM? For this kind of stuff you need to load up a bunch more info.

[Rawze]

Also the 553 code is not normal at all. Maybe a clogged screen in a return line .. or too much return flow due to leaky injectors?

Will it pass an injector leak-down test?. If so, what is the leak rate in one minute at 29,000 psi?
ref: https://rawze.com/forums/showthread.php?...3#pid75483