It appears you were about to say you have a Bosch system (vs Regina). I also see you live in California, in which case you are probably correct, plus your car is likely equipped with an EGR system. According to the 700/900 FAQ's, that code indicates a Lambda too rich or too lean condition, which can be triggered by any number of things. If the car runs good and is still getting good mileage, you might want to clear the code and see how long it takes to reappear before going crazy spending a lot of time and money trying to fix it. If it's really got a problem like a bad EGR valve, etc., it will likely produce bad numbers at the next emissions test. I would first see how long it takes for the code to reappear - but then then I'm cheap and lazy.