Hey, I finally figured out why my 2004 Z4 3.0 SMG was running rich in Bank 1 and Bank 2 It was the k&n air filter. Removed k&n air filter replaced with stock air filter . No more rich condition and no more SES light !!!!!!!! I know a lot of people use the k&n filter and have no problem, guess my car just did not like it. Later all !!!