To the O.P. I question the quality of this "$80 Napa pump from EBay"
Was it a Napa brand pump that someone had and then sold to you? at that point, who knows how long the pump sat on a shelf. I've had issues with new pumps on not common vehicles before. My only assumption is the pump sat on the shelf for some time and the rubber parts dried up.
Also, water, heet and a can of sea foam, all in one tank, I'm not too surprised you are having issues.
Was it a Napa brand pump that someone had and then sold to you? at that point, who knows how long the pump sat on a shelf. I've had issues with new pumps on not common vehicles before. My only assumption is the pump sat on the shelf for some time and the rubber parts dried up.
Also, water, heet and a can of sea foam, all in one tank, I'm not too surprised you are having issues.
Again, no surprise a no name pump is not flowing like it should. I would get a name brand pump for your truck before messing with trying to swap in a universal of some kind.