Exaust gas recirculation valves were introduced in the car market as a way to reduce gas emissions. Manufacturers created a way to recirculate already burned exaust gases over to intake manifoild in order to be re-burned and this way lowering their emissions. This is basically the function of a EGR valve Main problem of this concept, is that this exaust gases bring a lot of engine oils and fumes, that after sometime tend to block the intake manifoild lowering its efficciency dramatically.
This option allow tuner to close EGR valve all the time avoiding the build up of dirt in intake manifoild and all troubles associated with that.