Does the ecu need both o2 sensors, or can I disconnect the rear anD screw on the wideband? Idc about cels, btW

 

The second 02 is for emissions so not needed for performance, but I believe you NEED to connect the wideband to the first one. The exhaust gas after the cat is already cleaned therefore "tainted"...unless you are catless.

 

If you put your wideband in your o2 housing you'll burn it up fairly quickly and they're not exactly cheap to replace. Remove the rear o2 sensor (disable it via ECUFlash and Tephra hacks) and put the wideband in your rear o2 bung.