tlab,

I've been searching for the perfect exhaust for 6 years. I've had a lot of help as one of my good friends owns a muffler shop here in Vegas. After several trials and errors this is what we've done:

First, we decided that 2.75-inch piping is best; anything more and you lose vital back-pressure. We tried 3-inch piping, and we've also tried no catalytic at all. Torque suffers greatly, and I wouldn't go back to it.
After more testing we mounted a tiny, Borla catalytic (the same ones used by the "rice racers") as close to the manifold as possible, to generate heat as fast as possible.
Then we used as straight a shot of pipe as possible and tried a Dynomax Turbo muffler. This muffler choked the hell out of engine and the sound.
Then he says Dynomax came out with a Super Turbo muffler which had specific baffles that directed the flow more efficiantly.
He welded that on, and if you've seen my signature I haven't changed yet. It works for me. Good sound, good torque, and it doesn't choke at hight RPM. I'm very happy with it. And I've never had a problem getting it to pass smog.