it does come with instructions but dont be suprized if you do have to play around with it to get it right. some prople just jet it how it says and just forgets about it, but i did mine so i would get the most power out of mine. BTW your gas mileage will go down alot if you put in a big jet, i cant really remember what i had in mine but i do remember my gas mileage was around 45MPG. a person i ride with had a rubicon with a jet kit and he got around 50-55MPG, its just how much power you want out of it.
-Aaron