I put a pre-OEM filter on my truck this weekend. I installed it at the second alternator position on the engine. When I broke the line between the OEM filter and the EDU naturally the fuel line drained down to the frame. Before putting the new filter on the mount I did fill it, but all lines were empty. I started to prime the system, but after a couple strokes and getting a bunch of foam I decided this was going to be a real PITA. Closed the bleed valve and though, "I'll just let it idle 'til it dies and then prime it". It never died and has been running fine ever since. Looks to me that the 2004.4 LLY engine fuel system can tolerate quite a bit of air and can, in fact, prime itself. I used a WIX filter base, wh ich does look alot like a permacool head and a baldwin BF7633 filter.