The intake manifold gasket can fail causing vacuum a leak and/or a rough idle condition. Replacement of the leaking gasket will be necessary to correct this concern.Google+
Car Problem Reports
Mazda 626 Intake Manifold Vacuum Leak Causing Rough Idle
Mazda 626 Problem
Model Year Affected: 1998
Engine Affected: 2.0L 4 Cylinder
Visitor, 1998 Mazda 626, 2.0L 4 Cylinder, 175,000 mi
Surged to the point of stalling. I ended up spraying carb cleaner at the point where the intake met up to the head and found when spraying the carb lceaner at the no 1 cylinder, the engine speed noticibaly changed. The Intake gasket was replaced and the issue was resolved.