I am wanting to stay NA but am unsure about my exhaust. Would it be better to just upgrade the Y-pipe and the single pipe, or go with the true dual? I have seen some exhausts where it just has a single muffler too, would that be good for saving weight? Would there be any power gain difference?

 

Look at the design of the OEM exhaust, and study several aftermarket exhaust systems. What design do you favor? One that goes from the cats to the rear of the car with limited bends, or one that twists and turns like a snake? You can piece together your own ideas, or buy a cat back with proven performance gains.