Here is a graph I found of your 2004 CRF450 vs my 2006 YZ450F, I ended up getting a few more hp on top above 9,000rpm due to a modified full system Leo Vince exhaust, degreeing the hotcam for top end and some good race gas, but the bottom power never came up. The Honda's always made great horsepower and torque on the bottom end and this shows on the dyno below 8,000 and more importantly at a track like IMI.