Hello, I lit the MKL in my A4 B6 1.6 90tkm, can’t explain why. I had the error deleted and after 40-50KM it started again, when I drove on the bypass road very quiet 70. The Bosch service has the error : P0420 Catalyst System Bank Insufficient effect, this can be very much from air mass meter, throttle valve, false air to the defective KAT. I looked at this today and found the following what the previous owner probably gemac On the first photo it is drawn yellow, it has broken away the nose and so it holds a cable tie was made around it, can it be that by such a minimal a mistake is created and false air is sucked in? On picture 2 it is white made where the part sits, between air mass knife and throttle flap.