These are the symptoms as I remember them in chronological order
3 weeks ago fill up with fuel noticed that I did not get regular mileage it was worse.
Seemed like a minor loss in power
When cold and driving slow up a hill (out of my neighborhood) the engine would all of the sudden be noticeably louder.
Today wife drove home stopped and parked. Came back to truck it was hard starting as in you had to hold the ignition longer then normal to get the truck to start. If you just started it "normal" it would sound like it started and then die.
When started it was major loss of power. Boost was very low.
In park with engine running, if you revved it up when the rpms dropped it would stall.
I swapped the spare CPS I had in glove box. NO change. I changed the oil filter and oil, no change. I change the fuel filter no change.
High pressure oil pump was replaced less then a year ago.