Sorry to chime in late here but I have a couple of tidbits you might want to take into account for your exhaust purchase.
1) the scavaging of the exhaust happens in the manifolds/headers and then the rest of the exhaust helps keep that flow going.
2) if you go with true duals an H-pipe or X-pipe in the middle will help equalize the pressures b/t the 2 sides and help with the scavaging effect (due to the firing order)
3) Your pipe diameter is also important if it is too big then there is not enough backpressure and you will actually loose power and for single exhaust you want the pipe diameter about 1.5-1.75X the size of duals (most aftermarket exhaust companies already done the calculations to find the right diameter for you application)
I would look for a quieter system by law they are required to meet a maximum 95db level to be street legal otherwise it will be for offroad use only. I like the sound of flowmasters quite series mufflers when at WOT or part throttle you can hear it pretty good outside the truck it sounds good plus at cruise speeds it sounds almost stock no annoying drone or excess noise.
My $.02
|