Fuel smell, charcoal canisters, and me

[Bowtie001]

OK Everyone. I have a weird problem that pretty much everybody else has had. I couldn't find very much information by searching - so here goes.

My cab smells after sitting like gas - fairly strong. I had the seat out last weeknd and replaced all of the rubber line in the cab and replaced the clamps too. I found the vent thingie that goes up the B-pillar, and was confused. What does it do? I know that the tank vent eventually leads back to the charcoal canister -and I know what that does. Has anyone every had one of these leaking before? Can I bypass it? The answer to that is obviously 'no', because GM would have done that too.

OK, what do I replace next: O ring around sender, vent tube thingie or under cab lines?
I can't see how this would be the cap - it doesn't seal- this is obvious, but neither does the replacement. Wouldn't that make my garage smell like gas instead? Same goes for the fuel nech/cab gasket - why would that make the interior smell?

I hope this is not going to end up being the tank - I don't have the $$$ for this.

Thanks in advance!!

-Brian