I've been thinking for the last few minutes about some experiment I want to do, & I have some questions. I've got an 07 wr450 with a 2006 stock yz450 muffler & a pro-circuit stainless header that was supposed to be designed for the 06 yz450. The bike has good power, but I'm always thinking of things to do to it. So I've got a practically brand new stock 08 header sitting in a box, that thing is way fatter than the PC header. So I'm wondering if I would benefit from modding the midpipe on the muffler to accommodate the 08 header. Would the larger diameter of the 08 header add low/mid/top power? or would it possibly rob power from the motor? Any ideas? I know the shorty 08 muffler is crap, but what about the header?