Hey brother, Im doing the same thing with my FZ1, but im going the low mount way. From all that I've heard, you can just leave it alone, but you may lose some low end grunt and responsiveness. Ivan's jet kit will bring back that. The slip on alone will increase your mid-range and high end, and if you do the jet-kit, it will increase power through the whole rev range. I already have my slip-on, and have the jet kit in the mail. If you have money to burn, get it dyno tuned as well. Good luck friend!
Yeah, have fun! I an going to have my micron on for about a week before my jet kit is on also. Even if it runs fine, im still doing the jet kit. I don't want to run this thing too lean for a long period of time, which is what will happen if you run the slip-on without adjusting the air/fuel mixture. I'll let you know how it feels though after this saturday.
I added a micron slipon and I have installed ivan's needles. I've had it with and without needles. I say if you have the extra money then get the needles. It will run smoother with them! At least mine does! /images/icons/smile.gif