Okay I got a air/fuel gauge. I have a catless downpipe and would like to know if that will effect the performance of the gauge. All I know is that less cats more Carbon monoxide is produced, but does the oxygen sensor only pick up the amout of oxygen or the carbon monoxide also. Any specific facts I would appreciate greatly, Thank you! Ken

 

i have an 02 wrx with headers, up and downpipes no cats nowhere i have autometer a/f and i have no problems, btw all the stuff was install a year after i put the a/f in

 

I'm assuming you got one of the gauges that taps into an existing 02 sensor. The sensor that gets tapped is the rear 02, which is a narrowband sensor and does not provide actual A/F readings. Normally that sensor is behind the cats as well, although this won't be the case if you have a catless downpipe and uppipe. However the lack of cats still won't make the gauge accurate.
The only way to get true, accurate A/F readings is with a gauge that uses a separate, wideband 02 sensor.

 

The only way to get true, accurate A/F readings is with a gauge that uses a separate, wideband 02 sensor .............very true ...........very true...................