It's commonplace in diesel applications. Honestly not a lot of magic but there is the additional cost of adding the EGR cooler and the coolant loop associated with it. Most of the forum members think EGR is of no value but fail to realize its purpose. EGR helps to cool the combustion chamber because it is inert. In our application EGR only functions at part throttle, as such is helps cool the combustion chamber. When you go to WOT this will aid in prevention of detonation. Liken it to running a cooler spark plug or richer A/F ratio.
Neal