Fuel Pressure Delivery Warning and Check engine light

C7 Cat engines have a pressure regulator on the fuel return fitting at the rear of the cylinder head that can fail causing low fuel pressure. depending on the type of failure it can cause low pressure at low or high RPM or both. If my memory is correct fuel pressure should be in the 50 to 60 psi range at idle and 70 to 80 psi at governed speed.
I would also change primary and secondary filters and use genuine Cat on the secondary.