Header O2 questions

[silvasentra]

I was looking at replacing my headers in my 05 1.8 sentra but i have a few questions. Does anyone know if when you hook them up are you bypassing one of the cats? and is there still a hook up for the O2 sensor with resistance to keep codes and check engine lights?

[nametakennow]

The stock manifold has a precat, so replacing it removes that. You have to move the O2 sensors back behind the main cat or use a resistor mod to get the ECU to think it has an OK signal from the sensors.

I say sensors because I believe the QG has two banks of two, and the front two you will need to move.

[VMPhil]

that is correct the QG has 4 o2 sensors.