lab2370

The paperwork for when it had it worked on was from a Subaru dealership so I'd assume it's OEM

Hmm I'll have to try that. As for the Cat, I bought the car used (only 2k!)and it was already running rich but the guy had had the Cat done about 40k miles ago complete with paper work. So it SHOULD be good, doesn't mean it is though.

It's actually an Oregon care and definitely a little rust in spots. I guess maybe a tiny exhaust leak is possible, definitely dont hear any major leak. If it were an exhaust leak then it would like to be pretty far up the exhaust correct? Close to the engine if it's causing problems before it even hits the first 02 sensor?

Thinking it was an AC delco sensor

2009 Legacy, basically stock. It Started with getting a an intermittent P2096 "Post catalyst Trim System Too Lean Bank 1" And could smell it running a little rich Eventually code became consistent and ran very rich. Then it progressed and started throwing these codes P0137 " 02 Sensor Circuit Low Voltage Bank 1 Sensor 2" and P0031 "HO2S Heater Control Circuit Low Bank 1 Sensor 1" And now finally it's to the point where its causing a misfire in cylinder 1.I replaced both the pre and post cat 02 Sensors which didn't seem to help. So anybody got any ideas on what to check next?