Cool, I'm going to try the stock header.
I did a 500 mile 3 day ride in the dez and see what you are talking about. The bike screams in the upper top end but you have to rev it good to shift. This got worse on day 3 in the desert when my air filter was super dirty. on top of that i'm running 15/48 gearing so the the gap between gears is pretty good now. (the ratios are closer for the 03-06 than the 07+ bikes.
Bike has yz cams and a full Ti PC pipe that was on a 03 yz450. I'm not sure if the older pc pipe will slip on to the stock header though. It has no clamp at the joint. I also have a smaller end camp I could use.
I think the port job is in my future but I need to pay for a wedding and house projects first.
This was EXTREMELY noticeable for me with the stock porting and piston and header.
I could loosen the dirty air filter away from the airbox for a street test ride and gain 5 more hp below 6krpm....or of course, clean it....
I briefly rode Ken's around the block after his work was done, and it was fine. No issues that needed to be addressed.....but mine does have more power way down low with the added porting, if I can even remember anymore...
Edited by Krannie, November 13, 2013 - 02:14 PM.