Ok yall im stumped. I have a 2003 chevy 2500HD with the 6.6duramax. I have replaced the injectors and hard lines along with the fuel filter head and fuel filter but now i am constantly losing prime. I had it running after the injector change for about an hour then it would shut off and continually get air in the lines. I put a new filter head on it and it primed first go around and started right up and ran for about an hour and a half. About the hour mark it started to surge about 200-300rpm. Once i turned the truck off and tried to start it again i had lost all prime and it was back to doing the same thing the other filter head was doing. Does anyone have any ideas of what my problem could be? Im at a total lose my truck has been down 2 months already because of this issue.