If your motor is running rich ( you can smell fuel in the exhuast)
Or its just running like a bag of spanners.
Replace the Lambda.
Not so easy to do due to it practicaly welding itself to the cat.
First up this is a lambda,
Welly has attached the following image:
________________________________________Life is a lie. The only certainty of which is death. Go live and enjoy yourself. The clock is ticking