Has anyone used one of the kits? What exactly comes with one? I'd like to get as much power from my 96 Sportsman 400 but if the kit comes with just main jets and needle I can save $40 buck and get them from a local dealer.

 

I just put that kit on my Yamaha and it included three jet sizes, a new needle ( taller, thinner, more notches), and a small stainless spacer washer. I believe you would do just fine going to you dealer and saving some bucks. It comes with some pretty good diagnosing tips if your jetting is off a bit. Hope this helps.