Do you need the sensor going into the downpipe if you have an aftermarket computer? If so how do you get into one to replace the wire?

 

If you have a power FC (or other standalone, but not sure about others) and have your O2 feedback function shut off, then you won't need your stock O2 sensor. If you have a stock flashed computer, then you still need it.

A new one comes with a wire attached and most of the time a harness for the stock location.

 

How do I turn it off on a power fc? How much would an o2 sensor cost and would it do anything?