So, you have a fuel delivery issue.
Now when you turn on the key, are you able to hear the fuel pump prime for a few seconds?
It is possible to have a faulty fuel pump even if it is new.
Another possibility is having a clog in the line or a bad fuel pressure regulator as you are suspecting.
Have you changed the fuel filter when the pump was replaced?
I have attached the fuel pressure regulator replacement guide below for your reference.
Let me know of any questions.
Images (Click to enlarge)
Wednesday, July 6th, 2022 AT 4:10 PM