Just picked up new 2009 S3 yesterday love it! it has been remapped with a milltek exhaust the garage had,no paperwork for exhaust etc he was going to chase up anyway on way home engine management light came on dropped into local audi dealer for system check-it came up- catalyst system,bank 1 efficiency below threshold static?does this mean a new sensor required or need remapped has the cat been removed ideas guys ,salesman at garage is chasing up said there was no problem before my luck he will pay for what is required any ideas guys?