Why does my pre-Nov 18 1997 GTS has a very rough idle, or a very high idle?
A new Intake manifold gasket fixes this "driveability" complaint. Pre 11/18/97 GTS’s used an intake manifold gasket that turned out to be susceptible to moisture damage and subsequent air "leaking" into the manifold. This causes a lean, HOT burn in the cylinder(s) affected. IF you drove the car a lot (500+) miles with a raging leak, a valve or piston could be burned. A simple boroscope can be used (when the intake manifold is off, ) to look inside the affected cylinder and look for potential damage. It may be a good idea to have this inspection done BEFORE replacing the gasket.