I have a narrow band prosport a/f gauge in my STi and for a while all I thought it was good for was a pod filler and light show. Turns out though it was actually reading a bad O2 sensor and when I replaced that it did alright in steady throttle and WOT. Still it's only purpose in life is to tell me if there is something very wrong if it's all the way rich or lean, that's about it.