The tuned kit does NOT come with the upgrade Diffs, I am not sure what exacly is and is not included but you are probably better off getting the cheaper kit and adding the parts required.
Basicly the you will want:
hop-up diffs
turnbuckles
CVDs ( atleast for the front )
high speed gear set
reinforced prop shaft set
aluminum motor mount
front and rear shock piston sets ( you don't need the aluminum shock bodies )
Aluminum wheel adapters are a convience worth the money but they do not improve the cars performace.
Mark