09 zx-6r
 

I found out if you take the slip on off you get less pull out of the whole but not to much but after about 6,500 rpms it screams and you get faster acceleration its that way for me if its any different for anyone else let me know what it does thanks :)

it goes back to the exhaust basics. No restriction will alter the exhaust pulse waves in relation to the intake waves. So any change will affect the entire operation on where you prefer the power to be. I would think that a 6r should be more linear in the power curve and deserves a tuned system.

You need backpressure. Unless you want to ride around at red line everyday :)

Er...keep yer can on the pipe. Your neighbors aren't amused.