I changed the front sproket from the stock 17 tooth to a 16 tooth, and lowered it 3". Thats all the changes, otherwise it is stock, ran 23lbs of air in the stock bridgestone rear tire on that 9.9 run. The bike could do better with a lighter rider, I weigh 180lbs so I am not the lightest rider out there.
WIn43win, 9.90 is a good time, but I think something is not right after the 1/8 mile. I think with a 1.59 60 foot you should be in the low 9.80s. I have a buddy with a 2002 That had 1400 miles on it bone stock except front strap and he went 1.63 60 foot 9.86 at 142, and he is 210 without gear. Just wondering if your getting tucked down enough.