When I took mine apart, there was only one o-ring. The new filter came with two so I asked the dealer tech about it and he showed me where it was supposed to be on the bolt, and it actually made sense.

There's more of a story to this. I first installed with only one o-ring but then had a problem with hard start due to air leak in (no fuel leaking out). Thinking this was the problem, I took it apart and put the second o-ring in per the tech's instruction. Problem did not resolve.

And yes, I have replaced every hose and o-ring in the engine compartment. Can't find any leak anywhere but I'm thinking of taking the tank filter out (why?) and guess there's a check valve someplace. But I don't really think that will help either. The air gap that appears is in the line from the strainer next to the main filter. I can always see air cavitating in that line when running and have to park the car level or nose down. Nose up in the drive for more than a few hours and starting is a 10 minute starter workout.

Preventive maintenance... Should have left well enough alone...