Hello , I have a Land Rover LR4 V8 2010 that keeps giving a DTC when scanned

On starting the car, it sets a code
P0013-13 (Exhaust B camshaft position Actuator Bank 1)While idling it sets another code.
​​​​​​P0087-00.(Fuel rail/system pressure low).

Then if you switch on the AC while idling it set P0013
P0088-00 (fuel rail/system pressure high) and P0087 (fuel rail/system pressure low)

The Camshaft Actuator has been changed and still no difference. The Fuel pressure sensor has also been changed.
All wiring from the Camshaft Actuator to the ECU has been check for open circuit but there is none.

I also noticed the code is set immediately after ignition is switch on which might be an indication that the fault is form the ECU.
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Please can anyone help on this situation.
Thanks in anticipation of your response.
Lumidee.