July 2018 update:
Kept getting CEL that the gas cap needed to be tightened. Forum research led me to believe it was the fault of a few small hoses in the engine bay... NOPE
This tiny hose is crapping out
TL;DR The charcoal canister is cracked, that's the CEL. BUT they also noticed that both the MAF sensor and O2 sensor need replacing. Wideband O2 sensor is fine. So they replaced the O2 yesterday and will replace MAF sensor today.
AFRs should return to 11-13 under load.