Woot Woot....those are some epic photos and sounds like a great trip.
Also, I would disregard the CEL.....well not disregard, but consider that the CEL is NOT related to your aux fuel tank install. I've been getting some random CEL for bank and evap at less than 1/4 tank, higher RPMs (highway speeds), going over higher altitudes or when the engine is under heavy loads. Don't ask me why I'm just telling you that I keep a log and the conditions of all four CEL over the last 6 months have been the exact same condition.
Just food for thought for something for you to monitor.