I used the '04 R1 throttle tube. Definately shortened the travel needed to get to WFO. One slight drawback that's not mentioned often is the increased effort needed to twist the throttle. I noticed it immediately after doing the mod. Not an issue around town but if you do any longer trips with it you'll want to add a throttle lock of some kind. I used the Throttlemeister with good results.
How difficult was the install of this mod?
Very easy! The only glitch is that you'll need to take a Dremel to a raised rib on the tube next to the throttle housing that Yamaha uses to help keep the grip on. If you use the Yamaha grips(the tube comes with a grip on it) you don't even need to do this. Be sure to take all the slack out of the cables when you're done. Consider this mod a must if you see any track action. Much easier to get to WFO!