Question: is the egr valve part of the engine

Answer: Yes, In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NO) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. This dilutes the O in the incoming air stream and provides gases inert to combustion to act as absorbents of combustion heat to reduce peak in-cylinder temperatures. NO is produced in a narrow band of high cylinder temperatures and pressures. Another primary benefit of external EGR valves on a spark ignition engine is an increase in efficiency, as charge dilution allows a larger throttle position and reduces associated pumping losses.