Just got back from riding the new 07 YZ450. It was a short ride and the bike is brand new and really tight. I loved everything about the new bike except the motor. Dirt Rider was right....the 07 doesn't have any beans down low. After looking at the outlet of the boat ancor they call a muffler I noticed it was about the size of what should be on a TTR90. I quickly installed an 06 tail section and I'm happy to report the bike is strong! The 07 is a great bike, just remember to replace the tail section. The new header looks to be a stepped design and should work really well with any after market muffler! Looking forward to riding the bike again and doing a full test on it in the near future! Hopefully the 07 KX450 will be in next week and I'll be able to do a side by side evaluation! I'm expecting a lot from the KX this year!