ISM CM870- fuel pressure

[SquareOne]

Have you checked the vents at the tank? Sounds simple, but I had a bee build a small nest on the vent of my driver tank, causing the passenger tank to suck down faster damn near running it dry. (I thought I was just getting phenomenal fuel mpg since my sending unit is in the driver side lol)

If you have a similar situation and the other tank vent is partially clogged, it may be creating a vacuum while driving, but slowly equalizing the pressure when the engine is shut off...

Sounds simple but I'd prolly look for simple 1st being that the truck is 16y/o