Hi, I have an 04 STi with utec/tuner along with fmic, intake, exhaust, etc. Recently after installing the ewg I started having a really lean idle throwing the p0171 cel even though I know the ewg couldn't really be causing this so I'm assuming it's the fmic/intake which I put on a week earlier. My cruising afr's are really solid along with wot pulls, just my idle afr gets up to 17-18 at times and sometimes around 20 after driving and pushing in the clutch. I was wondering if there would be a way to tune in order to get the idling afr down. Thanks!

Randy

check for exh leaks before the o2 sensor. I had the same thing. I was reading 17.5-1 at idle, but if I was on the gas at all, they were normal.

I'm assuming your talking about the first 02 sensor, correct? And that would just be leaks in the header, right?