The diff is fine,The R32 wiring is fine just change the injector plugs and run the 2 wires for the VVT solinoid then plug in the R33 PFC(can use R32), If you have an S2 RB25 you need to fit your RB20 coils and module to the 25(1/2 hour work tops)If you use the R32 PFC i can sell you a controller for the VVT cheap so it is still easy.RB20 box will be ok if you are gentle but if thats the case you would not want the extra power so change it if you can.