Bucking? In top gear at low RPM? Downshift.
Jetting/ignition changes will not solve a 'problem' that really does not exist. You have a race bike, not a cruiser. RPMs should be above 6K most of the time.
I run my '08 WR from 3500 to 6500 most of the time without issue.
The carb tuning, TPS adjustment, and new ignition was necessary to get it to run clean at all rpms.
I don't know what the OP is trying to describe, as he is not being specific enough about the problem, his jetting, throttle position, etc etc, and seems to be really confused about just what is bike is.
I would recommend him getting a SERVICE MANUAL from the Yamaha website, and to study it a bit.