Exhaust questions

I have a couple questions reguarding exhaust systems on our cars.

First, if a true dual exhaust set-up could (and I emphasize COULD) be put on our cars, would there be any power increases? I know that our stock exhaust is pretty good performance wise as it is.

And second, theoretically speaking, would an exhaust pipe shaped like an oval instead of a circle be any more or less effective in exhaust flow?

Dual exhaust would loose power due to backpressure. I am one of the very few members with a "dual" exhaust setup, as many exhaust places wont do this for you. I was told no 4 times, and the fifth shop did it. Hit me up on AIM and as me for a sound clip and pics. Also I really recommend 2gstratus.org for coupe v6 specific questions.