I have my Hahn Stage II kit installed, runs good etc etc. Only thing is I have a CEL. Got it scanned it came up as Upstream o2 Sensor. I thought if anything it would have been downstream because there is no cat. Had the guy at Autozone clear the code, and it came back a day or two later. Same CEL, upstream o2. I'm wondering what would be causing this? Should I just replace the sensor and see if the CEL clears? The car only has 8,000 miles on it so its not exactly typical for the o2 sensor to be bad already.. I'm thinking maybe in the begining I was running too rich and maybe it clogged up the o2 sensor or something. Any thoughts? Thanks.