More than likely you will need to rejet your carb if you add a pipe. I have not added my pipe yet but fully expect to rejet. The jetting controls the air/fuel mixture, just like a carb. The setting will depend on the pipe, elevation, if you change the intake (air filter), etc. Sometimes you just have to get a new jet then use the stock needle. If you need more help look in the how to section, I think there is a write up!