Why bother to mod a Riveria? Its a big heavy car that will never be a sports car, despite your best efforts. The Riv was designed to be a highway cruiser, and the supercharged version was developed to give some degree of power to a car that really should have had a V-8 put in it in the first place. The 3800 Supercharged engine is probably pushed to limits just the way it is, without doing any "mods" to it. The Riv was designed for the country club set, not to race the ricers with.

-Mark- '99 Mystique LS, totally original (including the original water pump and the premium stereo)! Bought new in December 1998 for $21,000. 208,000 miles