I had major trouble with the throttle response as well. I was riding a CRF150R then got the new YZ450F, I got arm pump riding from my truck to the track and had to pull off the track after four turns. My friend told me about a cam in the throttle, I called Sam at G2Ergonomics and asked him if he had a throttle cam for the new 450 and he said he did. It's not listed on his web page but I think it's the same as the 09'. I used the 400 cam which mellows out the initial hit the most and it work AWESOME. The bike is still hard for me to hang on too but it's 1000 percent better now. Sam also said he can make a cam that is even mellower than the 400 he sells. I've had five rides now but I may have him make me a super mellow one.