EGR Control Valve
WARNING: This page is about a different car, the 1994 Mazda Navajo and 1994 Mazda B4000. However, it is still accessible from the selected car via links, so may be relevant.
Bring engine to normal operating temperature and operate at idle. Disconnect and plug vacuum hose at EGR control valve. See Fig 1 . Engine should run smoothly. Connect vacuum pump to EGR control valve, and apply 5-10 in. Hg. Engine should run rough. If engine does not run rough, clean or replace EGR control valve.