ignition timing at high rpm

Hi All. So I can adjust the ignition timing on my bike up to 6 degrees advanced.  My butt dyno is telling me 6 degrees advanced adds quite a bit of low end torque (up to say 7K rpm), but it seems the bike is quicker at high rpms (7K-11K rpms) when I have the ignition timing set to 2 degrees advanced.  I don't know why that would make sense.  Could be that my butt dyno is not well calibrated and it's all in my head...but I was actually expecting the opposite to be true.  Any thoughts?  (bike details in my signature)