Fuel pressure

Well the problem has been resolved at long last. After going through multiple replacement NEW fuel pumps, I finally found a used fuel pump from an identical model truck which I fully tested prior to installing and found to meet operational specs regarding flow and pressure. Took the trouble to pressurize it and check the pressure next day and found it did retain pressure (lower but pressure indicating gas would be at fuel rail) Installed the pump a week ago and truck is running fine. No running lean codes. The lesson learned here I would say is that for the work required to remove and replace a gas tank for a fuel pump problem I will in the future test the replacement pump to assure that it will met the required operation. Additionally, just because it is new and just out of the box it is not good to assume it will function properly. Thanks for all the advice that kept me from giving up on this. If anybody wants tips on checking fuel pumps, I have some experience I am willing to share.