Linear EGR Valve
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
See LINEAR EGR SYSTEM under EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS.