Originally Posted by Psyk
Forgive me as I'm new to the MT world (my last WRX was Auto), but if I'm correct, the Subaru (Factory) Short Shifter kit actually replaces the stock linkage. The Kartboy SS is a shorter "shifter rod" providing for a shorter throw. Though I don't remember where I read it, someone put it well by saying that the OEM Short throw option and something like the Kartboy SS option pair to make for much better/shorter throws together.
This, but to me it's a waste of money. Yes the SPT SS changes the linkage as well:
But it keeps the knob @ the stock height (also, if installed @ port, it keeps you in the stock class for Auto X).
The COBB / KB shorten the knob height a tad as well.
If you have the money, do both I guess.