Subaru EGR valve

2005 Subaru Legacy, Client came in for low idle, stalls intermittently, hard to Start.

Check fault code from Engine Computer Module, There were 3 codes.

P0400 = EGR flow fault

P0301,P0304 = misfire on #1 and #4 cylinder.

Removed EGR valve, the plunger was stacked on open position. From our experiences the cleaning the plunger will only serve temporally fix. We replaced to a new EGR valve. Problem solved.