Right On! Gilly! Had similar issues with the CEL. Tighten the gas cap "fixed" it each time. Called 18004Mercedes one time and the associate told me to just screw it. Anyhow, during the clamp recall service, asked the dealer to pull the codes and it turned out to be code P2013. Dealer replaced:

163-476-02-32 Valve
916002-012100 Clamp
005-997-45-90 Clamp

it says cause 47155737/18893 Charcol canister shut-off valve leaking.

Looks working very well bt far.