Alright did my homework on RC51 dot org and Kyle Racing's site. I was planning on buying the billet flapper valve block off and the pair valve block offs. Obviously most people rave about these two mods. I did not, since I purchased the bike, feel any of the 5k-7k hesitation, nor did by bike refuse to rev up in the 9k range. After inspection of my bike I am pretty sure both mods have already been done. Here are pictures of both areas that lead me to believe they have been done, as well as not having the symptoms. Can you guys take a look at these two pics and let me know what you think? By the way, the bike runs flawlessly.