0171 and 0174 codes after fuel pump replacement

[LeighRay]

Anyone have an Idea whats wrong? After replacing my fuel pump on the way home my CEL came on. The codes are the all to typical 0171 and 0174. Ive checked for leaks replaced O2 sensors new fuel filter new pcv ran seafoam through the fuel tank with no luck at all codes keep coming back. Oddly enough if I run without an air filter the codes seem to take longer to come back. Checked for vacuum leaks with starting fluid with no luck. I am stumped on this one. Plan to do a fuel pressure test this weekend other than that im not sure what to do next. I have a 1999 Ranger 4x4 with 3.0 with a fuel system return. the Regulator/ is on the fuel rail. The original reason I changed the fuel pump was intermitant operation. No codes until the new one was installed

 

[LeighRay]

new data

fuel sys1 CL, usingHO2S

Fuel pressure reading at the rail is 22 -27 PSI and contrary to my first post I now believe I have a returnless full system. What I thought was the return was actually the feed to the other rail. So what is the other line that runs to the fuel tank pump assembly? I will test the pump pre filter when it cools down outside and likely will be pulling the bed to access the top of the tank sometime in the wee hours of the morning. I would like to test the regulator if I can locate it and figure out how and will test the pump directly when I gain access to the tank. Can anyone tell me the pressures I should be looking for? Best I can tell from the forums I shoud be seeing 50 to 75 with 45 being acceptable. Any input at this point would be much appreciated