I have tried reading around a bit, but didn't find too much info.

I am installing a wideband O2 sensor and I have a full 3" turbo-back exhaust, so no cat.

I planned on having the o2 bung welded in, then realized there's a nice spot to just run the sensor right to the rear o2 bung. I realize there will be a slight delay in readings (probably un-recognizable) but my question is:

Is it okay to run the WB o2 sensor right into the rear o2 bung and delete the rear o2 sensor?

 

rear o2 sensor regulates the catalytic converter so your check engine light would be on for a $10 bung. I would place it prior to the 1st 90 bend in the down pipe on the passenger side, run the harness along with the upper o2 sensor through the spark plug cover and in the cabin, If you do not have a welder AEM makes a weldless o2 bung (its a clamp)

 

I think the only cost would be a delay and lower temps..

 

I removed my rear o2 and run my wideband in the rear o2 spot. It works great for me, the delay is only .1 of a sec if even that much.

 

Would it be fine if the test pipe has a bung to run it there?

 

Yes