Item 7 from this Racefit link:
Important Information & FAQs
7. WILL I NEED TO ADJUST THE FUELING (DYNO SET UP) AND WHAT SORT OF BHP GAINS CAN I EXPECT?
Making changes to your motorcycle exhaust will not suddenly cause it to not run, lose power or be damaged – your bike will run correctly as it is. Generally there are power gains due to our exhausts being less restrictive. There may be more power gains if the fitting is combined other aftermarket fuelling products,
but it is not necessary and we do not recommend it.
Be aware that your motorcycle is a production item and is subject to manufacturing tolerances – therefore no two motorcycles are identical. The performance of your motorcycle is in effect a compromise to comply with various noise and emission laws in various countries.
Hence a good reason to go with Racefit