EGR Valve

Start engine and run at idle. Detach vacuum hose from thermo valve (vacuum amplifier on 2.3L Calif. models). Attach hose directly to manifold vacuum source.
Engine should stall or idle roughly. If not, turn engine off and remove EGR valve and pipe from engine. Clean passages with brush and wire. Reinstall items and repeat test.
If engine still does not stall or idle roughly, replace EGR valve. When system functions as indicated, return vacuum hose to original position.

Fig 1: EGR System for 2.0L Engines (Calif.)
Courtesy of FORD MOTOR CO.