The one's on top should be for (1)vent, (2) return line (if required, if not cap it). Just be sure that the one you use for vent does not extend to the bottom

So it sounds like you decided to use my old buddy

Kid...Vent? Where do you vent it, to atmosphere? Could I leave it open where it is with a screen over it or do I run this to the front charcoal canister? or??? :confused:

CPNEJR...your buddy came in real handy. I might use him elsewhere on my truck :D