Water in Delta P sensor ....

[SquareOne]

Judging off the red paint, doesn’t look like they’ve ever been changed. If not, it overdue for an EGR tuneup by about 300k.

As far as the moisture goes, possibly cold weather causing condensation upon shutdown??

Again, I would do a complete EGR tuneup with that mileage in order to make sure those components will perform as they are designed. That alone will create or destroy fuel mileage.