Here we go , relating to performance, what is the best mod. you have done and noticed a big improvement ...don't make a list, just the single best item that you really noticed an improvement in performance....? :BLAA:
........ now I can tell how bad the rear shock is.
Having replaced the rear with an Ohlins..... I don't think just swapping springs to one that is correctly sized would be enough to cure what ails the back end.... the OEM rebound rate is IMHO much to 'fast'. At least it was, when I had to ride that thing with the shock set full 'hard' to keep it from wallowing around.
Good damping rates, and the right weight spring make a world of difference.