I hate loud pipes, they freak me out make me cringe and can cause accident. Not good for any biker - which is riding every day and long trips. Personally, I am not a fan.
I have no idea how this would effect the KZ1300, as that would need to be academically researched. Based on other bikes, that would disturb the pressures in the engine resulting in actual power and responsiveness loss at certain rpm's. Would you feel it? Probably not. So, as Phil says, basically it's OK. But on the technical side, probably not good. Other engines need re-jetting. I will tell you - even displacing a vent hose on top of the carb on a Vmax to another place will badly affect the engine. The maker did lots of testing placing it right there for a reason, because of dynamics of air flow, temperatures etc. But would you feel any difference especially with loud pipes riding around town - my bet would be not.