I've been told both. I have seriously considered both. The reason I haven't is that I have normal size tires 26". Stock is 25" I have been told by many good sources that if you don't go 2" over stock you don't need a clutch kit. Plus, I ride with hondas that can creep so I don't want a higher stall speed. As far as the jet(carb) kit, the extra power would be nice, but I don't NEED it. If there comes a time I think I do, I'll buy it. It claims to get you 10-15% more power for like 55 bucks. From what Ive seen, my stock bike hangs with the best of them and I'm happy with it. I fear that extra power would compromise the longevity of the bike. So far I am happy with everything. If,or should I say, when I step up to a bigger tire(27+) I will do these mods. Until then, I will ride her stock and still make many people jealous. Good luck