If you are running rich, you either aren't getting enough air into the engine, there is a malfunction with the fueling system that is effecting both banks, or there is something in the combustion chamber that is causing the ECU to add fuel.

How is your mileage, power, does the car smell funny when you drive it? Start with the easiest thing to rule out and go from there.

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2001 E53 3.0 5pd