Throwing code P2A00 after installing stock cats
 

I've been having this code over the past month after returning my car to mostly stock. A little history first, previously I was running the following setup with no codes for 6K miles:

Berk HFC
Nismo Catback/FI Catback (FI for last 500 miles on Berk HFC)
HKS filters

Went back to all stock except for FI catback a month ago and immediately started getting the P2A00 error after about 50 miles driving, i reset the code and again it appeared. This error is described on my code reader as "02 bank 1 sensor 1 circuit range/performance". Now my initial thought on this after some research was, possibly a leak of some sort... but all gaskets were replaced new and we triple checked any leaks.. none, same with the intake. The error is supposed to relate to the sensor in the passenger header manifold as well, and this was never touched, or bumped by accident. It's also in a major PITA spot to get too.

One thing to note though, is when i was running completely stock a year ago except for a Nismo Catback, I added new HKS filters and got the same P2A00 code I'm receiving now. This went away though after I replaced them with the stock filters. Currently I am using the stock filters, the only thing that has changed would be the FI catback from my original setup. Would the FI catback considerably change the A/F ratio to throw a code? Besides cleaning the MAF sensors (which only have 18k on them) or replacing the O2 sensor, I do not know how to proceed on this. I highly doubt it's the sensor itself, just the lean/rich tolerances. Any thoughts on this? I dont want to take this to the dealer and start racking up charges for diagnostics, is there an easier way i can determine if my A/F ratio is out of spec? Thanks for all input.

The dealer shouldn't charge u for anything

Just let the car adjust to the new setup; you can reset the ECU and let it relearn the stock setup and that will most likely get rid of the code.

Well the ECU has been reset multiple times at this point and I've been driving with the code on/off for well over a month now, so if it were to adjust, it woudl have by now. How can I have my A/F ratio checked? Dyno shop?

just the FI CBE shouldnt set the code off. I have the FI and K&N drop ins and no cels. Now when I had my HFCs put on they messed with the steering angle sensor and that set off a cel but I cant remenber which code it was. But if they took the sensor off to back the stock cats back on and didnt line it up right when they reinstalled it that will mess things up.

An out of range code usually means the sensor or connector is bad.

On other cars I've had O2 sensor codes thrown when there is flex in the exhaust system near the cats. Did you replace the gaskets above and below the HFCs when you removed them and went back to stock?

Yes all gaskets replaced new when installed. Maybe the FI exhaust changes the A/F too much and is causing this? I'm not getting any performance hits or bad mileage, but it's more peace of mind at this point.

it might be more the intake now with the addition of the CBE but I saw no codes with my HFCs and FI CBE and K&N drop i ns after they fixed the angle sensor.