Curious, do aftermarket headers affect AIR/Fuel ratings ? meaning making a mixture more lean or rich ?

I know a good header could possibly reduce the combustion temp inside an engine, but can it affect af readings ?

 

A better flowing header will cause the mixture to become leaner.

 

Of course. That's why you add more fuel with top brand headers.

 

What should the A/F reading be on a prpoerl tuned motor?

 

its different between all motors.. it just depends on what makes you power but isnt too lean...

 

Well, what should it roughly around, I'm going to be messing with a wide band O2 and just curious what it should be roughly around.