If you have an after market exhaust, then you might need to shorten the vacuum line (a rubber tube) running from the cross connector for the two carbs (found under the gas tank) to the lower end of the frame. The tube runs straight back under the tank, then straight down the middle in front of the air box and the battery. Disconnect this hose and drive your bike. If it improves your performance, then shorten the hose, if not, then you have other issues.