[rwhite65]

Well, the A+ servo is something you can change while the tranny is in the car, while you have the valve body out playing with what ever shift kit you buy. This servo is much stronger (better spring) and helps the tranny shift/hold fourth gear stronger. Since 4th is what most people burn out of the AOD, for around 70-100 bucks it is a little extra help.

I have heard the input shaft is a good upgrade also, although I did not do it with mine.
Ryan