I am trying to install a air feul ratio gage in my 2003 mazda 6i 4 cylinder. I want to know what line to tap into for my O2 sensor. Does anybody know?

 

not a clue and what the hell do you want a air feul ratio gage for anyway. that is unless your planning on raceing the thing.

 

O2 sensor is on your exhaust (probably just downstream from the manifold)

A/F gage on a stock 4-cyl is nothing more than a light show.

 

i agree with everyone that has posted on this . It is just a light show and it seems like you just want ppl to pull up next to you and have them think you are boosted . Now if your car is boosted yes A/F gague is good . I just installed mine on my 07 MS6 . you tap the O2 sensor right before your cat . Hope i helped