Everytime I start my car and drive for a little bit the check engine light comes on and reads Cb- Oxy Sensor control limit, cyl #4-6 and E4 Oxy Sensor Adaption Limit, cyl# 4-6. What could be the problem????? Could it have anything to do with my new dinan exhaust?? My car is a 1998 4 door M3 Automatic.