fluid dynamics, venturi effect, and oxygen sensors.
 

I have a catless header and my downstream oxygen sensor has a spacer with a 90 degree bend. Anyone have any idea the angle in which the 90 should be facing in regards to the flow of exhaust gas that would decrease the reading on the oxygen sensor? Thanks

What do you mean "decrease the reading on the oxygen sensor"?

Got a picture of the spacer?
If it's what I'm picturing in my head, the orientation shouldn't matter. Venturi doesn't apply because there's no way for air that is outside the exhaust stream to enter the exhaust stream (except via the engine).

On my WRX I just used two spark plug anti-foulers screwed into each other; one was drilled out to make room for the O2 sensor. Stock placement worked fine, never got a code.

I think you mean to put a fouler?

Wow... I had forgotten about this. Foulers... to think that we still need this.

Whatever they are you got the idea.

I can take a picture tomorrow.

http://www.autozone.com/autozone/acc...er=730544_0_0_

anti fouler or non fouler is correct; they keep spark plugs from fouling due to failed rings