Car running rich, and DTC 17584 o2 sensor issue

[damunky]

Hey guys,
recently I got a code, DTC 17584 (P1176) - O2 Correction Behind Catalyst, Bank 1 Limit Attained , and I bought a new passenger rear o2 sensor figuring that would fix the problem. I put the new o2 in, and after about 100 miles the code came back (I kind of expected it to). Does anyone else have experience with this code?? Could it be a clogged cat? Or just the fact that the cats are high flow and that could throw off o2 sensor readings? Also, I don't know if this matters much but I spliced the new o2 sensor onto the old one's wiring, but that shouldn't make a difference as long as the wire wasn't corroded or anything right?

Finally, the car is running fairly rich, can the above problem contribute to this? Is it possible to lean out the A/F using Lemmiwinks or some other tool?

Some screenshots ->
readiness:


o2 sensor status:

Thanks

[obijohn22]

why is the car running rich? what are your mods?

[damunky]

why is the car running rich? what are your mods?

Seems to be running rich just from my observations of fume odors, some black soot on the exhaust tips and also subpar gas mileage.
Mods: ABT ecu, UUC VM1 catback, UUC downpipes

[RolledMySTi]

What do you consider subpar gas mileage?

[obijohn22]

your UUC dp's have eliminated the pre cats. this will cause the secondary 02's to read incorrectly unless you relocated them past the secondary cats or use plug non foulers. did you do this? You can also have a tuner code them out for you if necessary. EGT's and the coolant temp sensor are common things that can lead to a rich condition.

[damunky]

What do you consider subpar gas mileage?

Around 18-20 mpg at most highway, I guess it's not terrible but not great?

your UUC dp's have eliminated the pre cats. this will cause the secondary 02's to read incorrectly unless you relocated them past the secondary cats or use plug non foulers. did you do this? You can also have a tuner code them out for you if necessary. EGT's and the coolant temp sensor are common things that can lead to a rich condition.

There are cats on the downpipes, not sure if they are stock or high-flow, just know they are UUC downpipes (I didn't put them on the car). The secondary o2s are located past the cats for sure.. Also, is it strange that only one bank is throwing the code? Wouldn't the other o2 sensor also throw the same code if the cats/ flow was identical? just a thought..

[obijohn22]

Around 18-20 mpg at most highway, I guess it's not terrible but not great?

There are cats on the downpipes, not sure if they are stock or high-flow, just know they are UUC downpipes (I didn't put them on the car). The secondary o2s are located past the cats for sure.. Also, is it strange that only one bank is throwing the code? Wouldn't the other o2 sensor also throw the same code if the cats/ flow was identical? just a thought..

I do not think it is that unrealistic to have slightly different readings from 02's on different banks. they all age a little differently and their restistance etc does not change linearly with age....But how many cats do you have on the car? 2 or 4?