Chad (loco pony) probably knows more than info as far as could stuff goes. But some of us have had issue with the tank vent tube clogging/plugging. Creating a vacuum. Second fuel filter could be a culprit. I would guess different plugs would not be a cause. Hope it helps a little.
Btw kudos on being a Stillers fan. Born and raised in the 'burgh here.

Blue/White, Battery Relocated, 155/45's, AI removed, Cocktail shakers