EGR Valve
WARNING: This page is about a different car, the 1995 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.
Warm engine to normal operating temperature and operate at idle. Disconnect and plug vacuum hose at EGR control valve. Engine should run smoothly. Connect vacuum pump to EGR control valve, and apply 1.5-3.5 in. Hg vacuum. Engine should run rough or stall. If engine does not operate as specified, clean or replace EGR control valve.