That's it - the official Calvin and Hobbes XB!
I think we need to see a shot of the front, showing your flyscreen.
110 pound plus VAT, not cheap, but fit a Free Spirits belt tensioner.
You will not need to re-map anything if you modify only your exhaust, and leave the air intake as it is. Your bike will be able to adjust to either exhaust or intake changes (choose one). If both, then re-map.