Do all cars have egr valves?

Not all cars have EGR (Exhaust Gas Recirculation) valves. EGR valves are primarily used in gasoline and diesel vehicles to reduce nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust back into the engine's combustion chamber. While many modern vehicles, especially those adhering to stricter emissions standards, are equipped with EGR systems, older models and some performance or specialized vehicles may not have them.