I figured the final drive would be to high for the weedy NA 1.6L . What year S box do you have? The later box has a lower final drive but not low enough for rallying. MiniSport do a low?? final drive http://www.minisport2.com/mini-parts/info_FDRCG14.html for the S box. I have the Midland box (Peugeot) which 70LBS lighter, being a Peugeot box I bought a LSD and 5:1 final drive which should help the NA engine a little. Only problem with the Midland box is they break easily.