The 1991 3800 was a very good engine.
The newer ones are just as reliable but have intake manifold & intake
gaskets problems as you may be aware of. Scroll through this newsgroup &
alt.autos.pontiac and you'll hear all about the engines your inquiring
Much of the late 90's 3800's problem was due to a plastic Intake
manifold ( also called a Plenum ) and bad gaskets. With 200 HP and 225
Torque there pretty good runners. The supercharged 3800 has 240 HP and
280 Torque but requires premium fuel. Having the supercharger eliminates
the plastic Intake on top of the engine.
1991 Pontiac Bonneville LE