It doesn't improve the sound of the exhaust but by removing the resonators it allows a more audible tone from the intake at 10k rpm and above you really notice a change volume. When I put my hid in it was real easy to take them out but I don't think you need to remove the upper to take to get rid of them. They are held in by one plastic screw and they should slide out with a little finesse. The HRC kit for our bikes says to remove the boxes for more power when you add the cams, pc, and exhaust. But I did for sound.

 

does it work 4 a 2008 model???