2017 5500, 80k miles fuel rail pressure issue truck is surging and won't run

2017 5500, 80k miles.

Fully deleted the truck, head studs, valve springs, AirDog 4g2 last week.

First week out truck was doing great.

Then as it got colder, rail pressure was dropping.

Figured this was due to colder temps, but at 60-70* was a total dog and would barley move. Once tank was below 1/4 and fuel was warm ran fine.

Already have a BD Diesel fuel heater on order. But don't think those temps would thicken the fuel that much???

Put a fuel rail plug on also.

That was about a 3000 mile trip.

Now 300 miles on the next haul, truck wont run. Day started off fine, but have had a surging get worse and worse where now I can't do 30mph.

Idles fine, rail commanded pressure vs rail pressure pretty close on display.

No smoke colors from tail pipe.

Trying to move rail pressure is under 3k sometimes. But in park can get to 13k+.

Checked all the fuel fittings and wires.

Currently down trying to find a shop to work on it.

Any ideas?