I have this mod, I did have the S5 shift kit but when the car was turbo it would still slip on gearchanges, the new shiftkit stopped all the slipping and now I can chirp third.
Thiis kit keeps the auto much cooler than without it. If I turn if off I get overheating problems.
Here is the wiring diagram for the S3/S4 kit:
Hope that helps
Dan