Search dude, tons of info.

I'll do my best to summarize though. Yes some people have dual exhausts, but they are custom made by shops - there are no bolt-on duals. I don't know if a magnaflow or flowmaster is louder, I do think more people here have flowmasters.

I put an exhaust on first and it helped some, but when I added the intake really did make a big difference - I think it's a synergy thing (the two together do more than what each alone would do). It does make it louder, it did help power, it did help throttle response a lot, and the two together sound great. I've not noticed any mpg difference.