Join Date: Sep 2008
Location: Fruitland Park,Florida
About the only other thing I can think of is an exhaust leak before the o2's, that is pulling in unmetered air. The o2's are seeing lean exhaust because of the air and making a very rich mixture.
I would say look for vacuum leaks, but that would pull the unmetered air into the combustion chamber where it would become part of the mixture. Pcm would add more fuel to mixture, but not as much as you indicate you are getting.