On a 98 it is in the plentum on the passenger side under the map sensor. turn the map sensor 90 degrees and pull straight up.pcv should be underneath.
The PCV valve on a 2002 Pontiac Bonneville is located on the back of the in take manifold, however to get to the PCV valve you will need to remove the valve cover.
Sorry I am not sure how to describe this, but this is a diagram of a Bonneville and its in the exact same location,
how do you change a starter in a 1995 Pontica Bonneville?
http://www.modifiedlife.com/1995-pontiac-bonneville-car-radio-wire-diagram/
pcv valve-location-1990 Pontiac bonnevilpcv valve on 1990 Pontiac Bonneville---location -on passenger side of engine, under alternator, push over wiring harness wires, as this maybe covering from sight.
It's in the transmission.
help
You can find the PCV valve beneath the MAP sensor located in the plenum at the right front of the engine.
to the right
About 17 mpg (city)
Plugs, Wires, Air/fuel filters, PCV valve
Look at the bottom or rear of the radiator