VAG engineers carefully explained this to me on 1st March. Decreasing NOx emissions increases the amount of soot produced. To cope with this, the DPF needs to actively regenerate more often and uses diesel fuel to do this. For the engine to handle this without the car using more fuel, the remap alters the injection sequence, making the engine itself slightly more efficient - just enough to counter the extra fuel used by the DPF. To prove that the car is using more fuel, you would need to have kept a proper record of mpg, calculated on a brim to brim basis, that you can now compare to your mpg after the remap. Or, at the very least, you should calculate your fuel economy brim to brim now and compare that to the average for an Audi A1 1.6 TDI Sportback in www.honestjohn.co.uk/realmpg, which is between 51.2mpg and 57.4mpg (depending on engine and transmission). If your fuel consumption is substantially worse than 51.2mpg, then you have a case.