if you can get a cat-delete pipe its worth it , bit more noise and power ,
if you mod your pipes theres only a slight increse in noise , if you cut them in half and leave them open they will be quite loud,
I drilled the core out then put a 1 1/4 inch bafel tube back in .
the origanal exausts have a verry small tube for the exit , but 1 1/4 entrance so I tried to mach this, I didnt want a verry loud bike that you need ear plugs to ride with . I like the sound and noise level now.
you will need to get the corect tune from you dealer to suit , unless you have tune boy or simular