Well from snooping around on the net I've found this

"When optimal air/fuel mixture is attained (14.7:1), the combustion process creates several different nitrogen oxides (NOx) because the combustion chamber is operating at over 2000° F . To reduce the NOx emission, the combustion chamber temp must be lowered. So the Exhaust Gas Recirculation (EGR) valve (generic diagram 1.) recirculates the now inert exhaust gas back into the combustion chamber to lower the total volume of combustable mixture. This results in a slight loss of power. Too much EGR flow will result in poor fuel economy, rough running and increased emissions. Too little flow can possibly cause internal engine damage from overheating."

That's what it does, to hold off on replacing it or cleaning it shouldn't cause too much concern but don't wait for months.

Answered by jwalth02
4 questions asked