Spn 157 FMI 15

[Bexie]

My son has the truck, 2014 Kenworth W900 used 2011 Cummins ISX installed by previous owner in 2021.
Engine Overhauled last year due to cratered fuel pump.
He bought the truck in Feb of this year. It had been standing since July.
Had new injectors installed by the folks that replaced the engine in 2021 (pure coincidence that we went to them).
Put in the rings in the injectors (not sure what to call them so hope you understand)
Replaced fuel filter and separator.
Replaced Relief valve on the rail.
After each of these changes the truck ran for upto 250KM (150 miles) and then the code came back.
Each time this code comes up he loses the throttle.
Mechanic figured the cause was high fuel rail pressure causing him to lose the throttle. It would come back after a few seconds.
Actuator was replaced on the fuel pump (newer type without the ceramics in it)
Truck ran for 3 days and now code is back.
Truck has deletes and was (apparently) tuned at some point for higher HP, 620hp.
He has been told that if the code is cleared the ecm will default to 30000 psi and not keep dropping it to 25000psi. Not sure about that statement and we do not yet have the means to clear the code.
I bought an inline 6 and software but the software will not install correctly. Waiting on support from the supplier but not holding out much hope.
Thoughts and next steps?