the flowmaster will enhance the exhaust sound of your car, and help it flow a bit better, but youd never notice it...BUT most people use the Flowmaster designed for the Firebird/Camaro, and if you decide to do this youll need a reducer of some sort, that particular flowmaster is a 2.5 inch inlet, and your car has 2.25 inch piping....there are a few memebers running these, and there are some sound clips available, im sure someone will chime in with some links for you
a high-flo catalytic converter, will replace your existing catalytic converter while still allowing you to pass emissions, it will flow much better then the stock one, and should yield a gain in performance, the cat is the second most restrictive component in the exhaust so replacing it is usually a good idea if you want better performance, although some would disagree...it should also make your exhaust a bit louder
but i would suggest an intake.as have others. it should give you a noticeable gain in performance as well as a change for the better in engine sound.
2000 Oldsmobile Intrigue 3.5L DOHC V6 15x,xxx miles "The Forgotten W-Body"
shaved badges, Eclipse HU, Pioneer TS-A1370R'*, Pioneer TS-A6971R'*, 20% tint, cleared corners, Silverstar Hi'*, 9005 Low'*
Fenderwell Intake, Hi-Flow Cat, U-bend delete, GMPP Handling Kit, MOOG endlinks, and 12-inch front rotors
1996 Bonneville SE RIP 157,751 miles, totaled 8/29/05