Its for emissions, it will keep exhaust gases form getting recirculated into the intake manifold. I'm 99.9999% sure you will see a CEL with this. My OBD1 hatch threw an EGR code and our cars are much much smarter than that.
I thought all cars made in the recent years had an egr valve to reduce emissions in order to reduce excess oxygen. "The exhaust gas also increases the specific heat capacity of the mix lowering the peak combustion temperature."