From what I've read, the holeshot system with exhaust, jet kit and filter will add 20+ hp on the top end, just not 20 more peak horses. Where the power curve on the stock bike falls off dramatically on the top end, the holeshot or equivelant system allows it to make a bunch more hp on top. So, just semi guessing from memory, where the stock bike might make 80 hp at 10 - 11K rpm the aftermarket stuff might be pumping 100hp at 10K+ rpm.
Also, be sure to leave a decent amount of slack in your chain when you adjust it, especially if you ride two up. Bandits are a pain to get the chain adjusted right. You get it adjusted then sit on the bike and then the chain is way too tight. Other posts have adressed all this I believe.
Warren