I do not know what the stock busa aspect ratio is on the rear tire but if it is 190/50, consider trying the 190/55. Larger contact patch on the side and you can feel a definite improvement in turn in at any speed. The 190/55 is ~10 cm higher and it will tend to correct your speedo.
You might want to do some research and see if that will fit your rim. Just an idea for ya. The busa already turns in pretty good. It makes enough difference that the 190/55 might be too much for some.