Charcoal Canister?

The main problem with them is that as they get older and older, there is the chance the activated charcoal could be sucked into the innards of your carburetor (plugging things up) as the screen to prevent this disintegrates. That's why I spent a couple of hundred bucks on a rare NOS canister for my vehicle.

P.S.edit: And that is assuming the innards don't deteriorate while sitting on the shelf somewhere for decades.