o2 sensor location?

[e36widelip]

hey guys,

it's time for emissions testing and i got to put on a high flow cat. I was wondering about o2 sensor placement. will i have problems if i place the cat upstream from the sensor?

[techno550]

you want the sensor before the cat. your O2 sensor should be downpipe-ish anyway though. At least by not far past the transmission, at which point you're approaching the first real place to put a cat.