I wish I would of caught your post earlier. The filter head orings are prone to leak air after several years of service, so the good thing is that you replaced the fuel filter head for not just your recent issue. But I would of strongly suggested that you replace the 2 fuel hoses that connect to the filter head because of age . They get soft and collapse because the fuel is being sucked to the fuel pump(CP3). There is some simple preventative maintenance that you can do to help your LBZ run for many years to come. There is a lot of good suggestion in the maintenance section of this forum.
06 HD2500 CC SB LT3 LBZ
EFI by Rob, DSP5, EGR blocked, 4" MBRP cat deleted, Edge CTS, Bilstein 5100 and stabilizer, Titan 52 gal tank, air lift in rear, Helo Max w/Ridge Grappler LT285/70R17.