Tests carried out by automotive journalists have all highlighted the reduction in diesel consumption which is induced by the use of P-Tronic tuning boxes. If you consume less, you emit less CO2 and so you pollute less. It's logical. This is all the more true as the reprogramming of the injection as effected by P-Tronic power kits in no way alters the contents of the exhaust gas.
« The user pays less in fuel, and as a consequence emits less CO2 » - La Libre Belgique
You consume less fuel so you pollute less.