Not an A-body, 2005 dakota X-pipe or true dual?

I know its not a A-body, but what would be best for power/toque to economy for my truck? 2005 dakota 4.7L. Would an X pipe to dual mufflers or true dual be better for power and mileage?

4.7L is stock, small diameter headers, throttle body spacer, cold air, and might see one of those superchips.