I have a 2003 Dodge Dakota Quad Cab with the 3.9L V6. I was able to find a cold air intake on ebay for around $50 or so. You can tell a difference in the sound of the exhaust (because it's got more air going into it) and will get a little better gas mileage and a couple more horsepower. That is about the best & easiest thing to do. I also added dual exhaust a couple of months ago ($220 look around prices vary), and for a V6 it sounds pretty good a lot better then I thought. Those two things I would suggest first. The dual exhaust you will have to take to someone to have them do it (welding, cutting, etc...). But the cold air into is just unbolt factory air inlet and box and then bolt the new one in. You can add new headers, which I have heard makes a big difference but you are looking at about $500 or so to replace your factory ones.