A TBB will boost FPS but generally speaking it wont improve accuracy. An upgrade hop unit like this will improve accuracy and if you get an H-nub with, as above, a Prometheus Purple soft rubber, it will be a lot better. An even better choice of nub is the ASPUK or RA-Tech type. From the sounds of it, barrel instability may be contributing, because your shots are going left and right. But something else to check with that is what BB's are you using?