I have rtecently bought a Japanese import 1986 gsxr 750.It runs well in the bottom end and the top, but has a stutter between 5-6000rpm when you crack the throttle wide open. it does not happen when you roll the throttle open steadily or when the bike is cold/cool.I have replaced both coils, cleaned carbs ,adjusted jet needles,adjusted accelerator pumps and balanced carbs. Is this common ? does/has anyone else experienced this? and how is it fixed without paying a fortune for someone else to play with it for hours? any help greatly appreciated