This was one of the best mods i did - night and day difference! I used the JD Jetting Kit, which is great because it tells you what jet to use based on the mods you made or are going to make (air box, backfire screen, etc.). I would highly recommend it. Very noticeable increase in the mid range. The bike also starts quicker and warms up quicker. I have a Cali bike, used the #165 jet and the needle was already set for me, I beleive in the 5th position. I have the air box mod, removed the backfire screen, white brothers air filter and white brothers E2 exhaust and pink wire mod. Totally different bike. I bent my handlebars so I just ordered better ones. We will see how they are.