Welcome to 2CarPros.
The code you have is related to the fuel rail pressure. I see you have replaced a few things already, so you already know what the code indicates.
If you look at picture 1, it indicates the possible causes of this code, other than the sensor or an issue with the regulator. Take a look through it.
With that in mind, have you checked for vacuum leaks? Although you have replaced the regulator, have you confirmed that the fuel pressure is within the manufacturer's specs? If the pressure is too low it can cause this too.
Here are a couple links that you may find helpful. I suggest you check for vacuum leaks and confirm pressure first. The pinpoint diagnostics for this code are pages and pages long. Hopefully, we will find it this way.
Here are the manufacturer's specs for fuel pressure.
Key on, engine off .................... 240-310 kPa (35-45 psi)
Engine running .................... 193-310 kPa (28-45 psi)
Check these things and let me know the results.
Thursday, March 21st, 2019 AT 7:35 PM