Exhaust Back Pressure??

Okay tech guru’s I have an interesting question for you…how much back pressure does a motorcycle really need??

I will clarify I have a 1995 ZX6c (Ninja 600R) and for a while I have noticed that my exhaust is far louder than most and that my exhaust can is never very hot, I started thinking that maybe I had a hole in my pipe so I checked it out…sure enough there was a rather large hole in the end can right were the pipe meets the can. I started to think about whether this “performance wise” was a good thing or a bad thing. Obviously bike motors need some back pressure but how much is enough?? Is having a hole in the end can actually beneficial (I am thinking to the old 70’s bike they use to straight pipe for performance and sound). I am about to put in a jet kit and k&n air pods and a 4 degree timing advancer but I am wondering if I am going to have to fix the exhaust pipe first to actually get the better performance out of it…but what do the pros think??

Any and all help is greatly appreciated