This O2 was put in in the exhaust when the turbo system was installed. It it isn't plugged into anything. It's after the two banks have merged together. I'm not running cats and still of course have the normal pre-cat O2's in. It's a Ford sensor (made by NTK) xc2f-9f472-a1a. Is this a wideband O2 or something? I tried Googling it, but no real info came up except for general app info.

 

My guess is that it was a place holder and plug.

 

Like mentioned above, its most likely being used as a plug for the exhaust. Rear O2's basically verify whether a catalytic converter is working properly and dont have any affect on fuel trims.

 

That would be weird as it's a completely custom exhaust that was made after the turbo system was in. Can't figure why the exhaust shop would put that there.

 

Because the shop that did it knows well enough that a good turbo setup will almost definitely use a wideband. They did you a favor.

 

Wait, is that a wideband sensor? Or you're just saying is a placeholder for a wideband 02 to be put in just when it's tuning time?