Usually when an O2 sensor goes bad, you get an O2 sensor high voltage error.

I see. Any ideas on what this could be then? Is it really just my tune?

Oh - what's your MPG been like? Has it been around an avg of 20MPH?

I honestly never monitor my MPG. I don't have a very long commute (maybe a mile each direction), so the only real miles I put on it are on the weekend.

You can check it on your dash if you scroll through the readouts. Anyway - I was just curious. If it was something like 35 or something - then you might be pretty lean....

I just saw a lot of people get 30. I guess I am a bit of a hoon.

Anyway GL!

Just checked and Avg. is 14.8. Not sure how long that takes into account though because most of my driving is city (SoCal, so lots of stop and go) and I have been to a track day every month for the last 3 months.

Was your intake installed before or after your tune? Was anything installed after your tune? Do you have any logs? Preferrably ones that involve a bit of driving (more than just a full throttle pull). I'll gladly take a peak for you. The AEM intake cheats the MAF and if you were tuned pre-intake and installed it your maf reading can be off thus leaning the engine out.

15AFR is normal under cruising / idle, the ecu goes into closed loop and will swing in certain ways for multiple reasons. Also going over 19AFR while engine breaking or engine decel is normal it is actually the ecu shutting off the injectors completely and the sensor simply doesn't have a readout for "no fuel".

14.8 AVG or 14.8 at that moment? There are two readouts. One for avg one for the currently being consumed calculation.

lol... Epic response. :P

That's the average.

How long ago did you reset that...???

And any logs?

I have never reset it manually. Unless unplugging the battery will do so... In which case about 2pm today. Haha

Removing battery terminal will reset ecu and clear DTC/CEL codes as well as reset learned fueling and ignition timing parameters and a bunch of other counters.

listen to @nelsmar you need to get some logs of general driving to see what going on.

as nelsmar said AEM intake will require MAF rescale or you could get problems and CEL codes you describe was it installed after tune ? also leaky exhaust gaskets near either 02 sensor or engine can throw readings off and cause rich/lean issues did you use new gaskets when headers installed if you re-use the originals they tend to leak after about a month. ??

If you can't do propper logs (torque is a bit slow refresh rate and cannot log all the required parameters) take it back to tuner before it gets worse and more expensive.

If it was me I would not be going WOT with that cel code coming up.

AEM Intake was installed before tune. Tune took intake into account. Brand new OEM Subarau gaskets were used for header and OP. I can take logs using ECUFlash software. What RPM ranges do you suggest I log?