I just bought a new 07 wr450 to replace my 04 wr450. The 04 has had all the free mods done, yzf pipe with fmf powerbomb front pipe, adjustable fuel screw and a jd jet kit. My 07 has the same stuff along with the ais removed but it has a performance insert in the standard exhaust and a yz front pipe. It doesnt feel quite as good, the power is still there but it doesnt have the kick of power my 04 had. What other bits can i do to give it more power and feel more like the 04? Is it the exhaust thats is making the difference?