The upper intake manifold gasket and/or a PCV vacuum lines/hoses can develop vacuum leaks with age. This type of leak can result in a higher that normal or rough idle.
Car Problem Reports
Oldsmobile Cutlass Supreme Intake Manifold and PCV Vacuum Lines/Hoses Can Leak Due to Age
Oldsmobile Cutlass Supreme Problem
Engines Affected: 3.1L V6, 3.4L V6
Average Mileage: 157,833 mi (117,000 mi - 190,000 mi)
Visitor, 1990 Oldsmobile Cutlass Supreme, 3.1L V6, 135,000 mi
erratic idle, loping
Visitor, 1995 Oldsmobile Cutlass Supreme, 3.1L V6, 185,000 mi
problem; overheating, power streing leaks and radiator will not hold water
Visitor, 1995 Oldsmobile Cutlass Supreme, 3.4L V6, 117,000 mi
engine began to idle at about 2000-2500 rpms
Visitor, 1992 Oldsmobile Cutlass Supreme, 3.4L V6, 140,000 mi
idls very low . when put in drive or rev. engine cuts off. i have to two foot drive so it doesn't cut off at red lights.