exhaust back pressure sensor issues

[S_Premo06]

fault codes are as followed,
2764
125
2448
2215- fuel pump has since been replaced and this code is no longer on
2554
2374

I removed the DPF and found it to be melted so I replaced it and driver did a regen on it, I was not there to watch the numbers so i'm not sure what temps it hit. The driver took the truck and made it to iowa from forest lake mn and the low boost light came on. there is severe black soot coming from the stacks.