ok it sounds like we've done the same things 2 our SV21's..... 2" all the way back high flow muff and K&N element filter.
After i put a 2" cat-back on the Kws jumped from 60 at the wheels to 66. 10% from just a cat-back! Anyway it goes soooo much harder now with the full zorst, but i have yet to dyno it. i'm going with a group of friends on the 28th of this month for a dyno day. i cant remember where right now but i'll ring my mate and find out. it's $45 for 2-3 power-runs.
hope that helps.
PS if u do do the cams let me know if the power difference way worth the price