Well thats a big debatable topic. EGR causes drop in engine performance. So the fuel which is supposed to burn more efficiently doesnt burn and this wastes fuel. To produce more fuel we pollute more Also the EGR in stock mode also operates in Part throttle. Anyways EGR is closed while driving in high rpms, so most of the time the car is polluting. So i have added only 2% to it which is compensated in burning fuel more efficiently.