Seen a lot of posts on the subject. Some with problems, most say it rips. My bike recently started feeling sluggish off idle, bogging with quick twists and missing sometimes on the top. Ordered the JD kit and a Zip Ty Air fuel to play with the tuning. Installed just as recommended for WR at 0 to 4000 foot. After adjusting the air fuel a bit,testing with quick throttle twists, I climbed on and did a quick test run up the field. The damn thing about jumped out from under me! Pulls like it never has throughout the entire range and throttle is much more crisp. Still won't handlle a full throttle twist from the bottom without a bog but much better. I'll look at the BK mod if I can't fine tune it out with my new air screw. I HIGHLY recommend this jet kit!