When installing an aftermarket exhaust, most times you will be required to re-map the fuel system to compensate for the additional flow provided by the exhaust. It will vary based on location, because the bikes will run differently at varying altitudes. Typically for the bike to run absolutely spot on it is a good idea to re-map. A lot of times after re-mapping you will see an increase in fuel mileage also. The most common FI controller is the Power Commander. It will allow you to re-map for the exhaust and changes are easily made in the future for additional modifications.
Just about all the Cobra exhausts sound great compared to the stock setup. If you are curious on what they sound like, you can log on to Cobra USA and select your model information. Cobra supplies sound clips of various setups to give you a good idea on you will hear. www.cobrausa.com