So, the high flow cats eliminated the p0430 code I was getting from the old OEM ones, but after a week popped a p2096 (bank 1 downstream lean condition).

I know it's not uncommon for some HFCs to throw a code without a tune. While many people have good luck with Kinetix because they use the factory O2 sensor bung position, i have considered they are the cause...but it does seem odd that it's only throwing a code for bank 1 and not 2 if that were the case

Possible culprits I've considered:

1) The shop I had do the install (not dealing with the demon bolts myself on a car that's seen a dozen northeast winters) replaced one downstream O2 sensor because it could not be removed. I don't know which one. While the bank 1 sensor still appears to function, could it's relative age be a concern? I graphed the voltages with the Torque app and bank 1 does indeed show lean and the bank 1 & 2 graphs are not symmetrical when cruising.

2) The gaskets that came with the HFCs were used (not sure of the quality). I have an appointment to check and re-torque everything after some heat cycles (also put on an S300 catback at the same time) and I'll have them double check the seal on bank 1 as I could definitely see a leak between the upstream and downstream sensor causing the issue.

Anyone have any other thoughts? Want to check all the boxes before dropping money on a tune. Maximum performance wasn't my goal here, just getting a little upgrade while not paying OEM prices for a bad cat and rotted exhaust on a 12yo car. (Mission accomplished even if I do have to tune)

 

When I did my HFC on my 04 coupe I replaced both O2 sensors at install bc of the many horror stories of them not working once disconnected at high mileage. Replacing the old one would be my first guess.

 

Thanks. It appears that the downstream o2 sensor that was not replaced is the one one the side with the problem. Having it swapped out today. At 140k mi it doesn't owe me anything. We'll see if that clears it up

 

Got under there and the bank 1 o2 sensor was loose. Tightened it up, cleared the codes, drove around. Trims look much better. We'll see how it looks in a week