Is the intake gasket a common problem on 1998 Buick century with 3.1 motor?

While not the *most* common problem on a 1998 Buick Century with a 3.1L engine (things like cooling system issues and ignition components are often higher on the list), a failing intake manifold gasket is a relatively common issue, especially as the vehicle ages. The gaskets can become brittle and leak, leading to vacuum leaks and rough running, poor performance, or even stalling. So, the answer is yes, it's a problem that occurs with some frequency on these vehicles.