Exhaust gas recirculation (EGR) is a nitrogen oxide emissions reduction technique used in modern engines. The EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders which intern lowers the concentration in the combustion chamber.
A faulty EGR valve usually results in the vehicle having decreased power and acceleration.
Nb. If the EGR warning light is on simply replacing the valve will not turn the light out.