My parents have my old A3 which has now got the check engine light on. The two faults codes that come up on VAGCOM are: 17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!) P1297 - 35-00 - - 17545 - Fuel Trim: Bank 1 (Add): System too Rich P1137 - 35-00 - - To start with I cleared the codes, and then 10 days later it came back on. The car has a jabba remap and also had a turbo dynamics recirc valve. The recirc valve has now been swapped back to a standard valve and the codes cleared, 10 days later the light comes back on. We have replaced the MAF and all the coil packs, cleared the code and 10 days later it comes back on. Any idea on what to check now? I've read that it could be the lambda or possibly the coolant temp sensor, or it could be a boost leak. The temp sensor was replaced about 2 years ago with a green one. Does anybody know how to test the lambda sensors with VAGCOM? Or what else I should be checking?