So, about 6 months ago I finished rebuilding a '02 WRX that had been sitting for a year or so. Now I keep getting a check engine light from the O2 sensor in the catalytic converter. The thing is, it has a Borla full exhaust kit and no cat. I had it in to a local dealership for a checkup a few weeks ago and they didn't know what to make of it and just reset the code. The light started coming on after I put about 2000 miles on it and if I reset it, it usually stays off for a day or two. Other than the weather the only change in that period was some adjustment of the BOV. The light has also mysteriously turned off on its own accord during long drives.

I guess the first question is would there be an easy way to prevent the code? Do you think there is something with the phantom sensor or is the BOV causing it to throw a code. The exhaust was done by the previous owner and I haven't really gotten under there to see for myself if there is a sensor somewhere or not. It has a Turbosmart BOV that vents to atmo. The car has quite a few aftermarket parts so it could probably use a professional tune. So while I'm at it, are there any good tuners in the Kalamazoo/Ann Arbor/Detroit Metro area?

I'm not the most experienced in these things, so any input you have would be appreciated.