More air in & out? vs Stock set up.

[rattletrap]

I have a 2003 dodge dakota quad cab with a 3.9 ltr. & 4X4. My question is.
Is it feesable to add a larger air intake system and go with a dual exhaust, to help in horsepower and fuel...compared to leaving the stock system on it. Does anyone have pretty close numbers as in horsepower improvement and fuel mileage? I am not a heavy footer, but I occasionally tow a 7X14 trailer that cuts my fuel mileage by 5 miles per gallon. I'm just looking for some ideas verses buying a bigger truck, which I really do not want too, because I like the truck I have.