Eric1,
I hate to break this to you, but I am still getting my 176 (front o2 sensor) code. Last week (before cleaning the EGR passages where they enter the UIM) I was getting 176 (front 02) AS WELL AS 172 (rear o2) and 332(EGR not opening). By removing the throttle body and cleaning the EGR passages I fixed the 332 and 172 codes.
In my case I believe the plugged EGR passages were messing up the ECC system and resulted in the 172 and 176 errors. As it is, I think that there is nothing wrong with my rear o2 sensors but maybe a bad front o2 sensor. I am told that there are actually four o2 sensors on the 2.5L (two on each exhaust manifold).
Anyway, I would definately check out the EGR passages(because they can get fouled up), but I wouldn't think that it would fix your o2 error. Please note that I am no mechanic. I could tell that there was carbon buildup on mine without actually taking the TB off - by looking through the TB (with the mass airflow sensor and air box removed).
