Have you tried testing if one of the MAF sensors is bad? They are quite sensitive so potential for damage is possible. I hope it was just bad gas but I do not think that would mess with AFR readings. A vacuum leak would make more sense if the car was idling high, sometimes comes with a code too but a code should also be thrown for a bad MAF. hmmmmm.... well, looking forward to this resolution, good luck!
Sounding like it was just bad gas, I'd avoid that gas station if that is the case.