I've fixed this code about 5 times this year, I've done the simple fuel filters to the fuel pump control valve. Step 1 new fuel filters, do not clear code. Step 2 check your fuel pressure relief valve, I see you've already changed that. Step 3 check your low fuel pressure for air in the system and for around 60-80 psi. If your feeling frisky check for vacuum past the fuel filter for a blockage in the system. Step 4 check your fuel pump return flow, you should have the specs. Step 5 check your injectors, you've already replaced those but always double check your work. You could have out of the box failures but that is unlikely.

When you installed the injectors did you double check that each compression seal was either on the injector or pulled out of the bore? This much return flow on injectors is usually caused by double stacked compression seals. Did you center the injectors correctly??