On a 1995 Buick Riviera with the supercharged 3800 engine (Series II), the PCV valve is typically located on the
passenger side valve cover. It's a small, usually black, valve with a hose attached to it. However, it's not always in the exact same spot on every engine, and sometimes it's a bit hidden. You may need to carefully look around that valve cover for a small, usually cylindrical, component with a hose connected to the intake manifold.
To be sure: It's best to consult a repair manual specific to your 1995 Buick Riviera with the supercharged 3800 engine. A Haynes or Chilton manual will show a diagram and pinpoint the location. You can also search online for "1995 Buick Riviera 3800 supercharged PCV valve location" and see if you can find pictures from someone who's already done this repair.
