Yea, that plug looked like a rich condition (and really not that bad of one) Also if you use alot of additives (or the gas you use does) will do that too. Buying gas from different places sometimes causes that. Personally, I only use BP and I use the "middle grade" because it's consistent. And I use STP gas treatment about every 4th tankful. Hell a dirty air filter can cause that + the fact of cold weather. Try tracing the wires going from o2 to DME - I'm suspecting a loose or "chaffed" wire sending a false signal (and ALL the ground leads)