On some of the early RZR's 07 amnd 08's the intake boots would come off the air box. The newer boots where made bigger so they had more flex. I put and CFM air box with K&N air filter on my 08 RZR. It worked perfectly!! CFM is one of your supporting venders check them out.
http://rzrriders.com/forum/cfm-performance-atv/rzr-cfm-air-box/