The vacuum-operated exhaust gas recirculation (EGR) valve is used on California model Jettas with engine code 9A (2.0 liter 16-valve) and on Canada model Jettas with engine code MZ and automatic transmission. The EGR system operates only at part throttle to direct a small amount of exhaust gas into the intake manifold. The exhaust gas displaces a small volume of the air/fuel mixture, resulting in lower combustion chamber temperatures and a reduction of certain harmful emissions. A thermo-pneumatic valve in the EGR system permits vacuum to open the valve only when engine coolant temperature is above a certain amount. A vacuum amplifier increases the strength of the vacuum.