Hey all, I'm having some kind of fueling issue going on with my 00 A6 C5 2.7 tip. Originally I did a nef1 tune to an L-box and put it on, but now I've reverted back to the original bin that I pulled while I figure out what's going on. Car is completely stock with 124k miles and I've recently done some of the usual maintenance items that needed doing. The only DTC is for catalyst efficiency below threshold bank 1, using vag-com. Here are some charts with the log as well, I can't quite pinpoint what the problem is but something seems funky with the readings from o2 sensor voltage and resistance. LTFT's are consistently within +-1%.

Thanks das, I realized that after comparing it to a good log I found. The thing that concerns me is my O2 voltage is all over the place, and running lean it looks like. There also seems to be significant differences of resistance between both pre-cats. Bank1S1 was replaced recently as it was giving DTC resistance too high. I should fess up and say it was a Bosch universal 4 wire #15733 and I didn't replace them in pairs. Thoughts?

forgot to add log.