Our experience on the 800 shows you can use the reed spacer. Air Box may sit in a slightly different angle, no big deal. They say to increase / decrease jet sizes: We saw no need to change jets. On top: Stock MJ are almost lean to begin with. Bottom end PJ: We increased the size to 20 like they say and the machine idles rich leaving a mark in the snow. Stock 17.5 was the right size.