Beat me to it.
I was just researching the function of the charcoal canisters and it seems they're a little more advanced version of that "vapor-liquid separator" in the diagram I posted. Helps filter fuel vapors so they can't enrichen the intake mixture.
I had been wondering about the "thing" too. I'd surmised that it was a valve of sorts, but the exact function wasn't yet certain without the manual. Thanks again for helping clear things up.