Which O2 sensors to tuners use to tune with?

[j0n]

I just installed some used off-road Kooks headers and the O2 sensor situation confuses me... Should I use the front(flat plug) O2 sensors or the rear(square plug) O2 sensors. The reason for asking is I bought O2 extensions from an online vendor and they are the square plug, but I was under the impression that the O2s that control a/f ratio are the fronts, which utilize the flat plug. I'm quite exasperated over the whole install and would love the help. Thanks in advance.

[Billf6531]

You're correct. The front O2s are wired via the flat connector. I recommend you use the rear sensors that you purchased (square connector) since they have better heaters to counteract the cooling effect of the LTs. All you now need are the adaptors to mate the square connector to the flat connector, and you'll be golden.