OK I am about down with my lt header install but which o2 Senor's do I use ? Top two or bottom two ? I am doing a off-road y pipe

 

The 2 front O2 sensors are used and turn the 2 rear O2 sensors off with HPTuner.

 

All narrowband sensors are the same. You can walk into any auto part store, buy any $8 1-wire, 2-wire, 3-wire, or 4-wire sensor from behind the counter (any price any vehicle) and use it in almost any vehicle/engine in the world.

 

OK I did a mail order tune from frost just was unsure which o2 sensor to add the extension to