I've got a 2005 GMC Yukon XL that shuts off all the time when I'm trying to put gas in it. I have replaced the solenoid by the evap canister and the one on the intake manifold so far (no help). Last night I dropped the fuel tank and couldn't find anything clogging up any vent lines. I pulled the charcoal can off and it seemed like it had oil in it? So, while I've got that down, what else do I check / replace?