exhaust gas sensor

So my car failed it’s MOT on the emissions. I serviced it 2 days before and ragged it to the garage. It’s an AMK on 145,000. The results were: Fast Idle Engine speed: Limit 2500-3000 Actual 2820 CO: Limit <0.3 Actual 5.1 HC: Limit <200 Actual 188 Lambda: Limit <0.97-1.03 Actual 0.87...

EXHAUST GAS SENSOR NUMBER 4 Hi guys I tuck my car to Audi yesterday for a ecu update and the tech in audi tells me that exhaust gas sensor number 4 need to be replaced. But he would not tell me where it is part number or anymore info. I would like to know firstly dose sensor number 4 have any to...