[slickwill]

It will definitely need a rejet. With a bore that much bigger it is going to need more fuel and more air. Open your airbox up in anyway that you can then rejet to slightly larger sizes to give the extra fuel needed. It can take a lot of work to get everything to work better together. You probably won't want to go back to a stock pipe because that is going to choke your airflow. As I said earlier a bigger bore needs more air and fuel you have to give it both and you have to get it to the right ratio. Take it to an experienced tuner and they should be able to get it running right.