i have an R32 with an RB25DET too, and id be interested in the speedo prob as well. Mine shows ~15km/h over the actual speed of the car.
e.g., the car will be travelling at 95k/h, but the speedo will show 110k/h.
i have to get the sparks changed and injectors cleaned (or get new ones), but atm with misfiring probs and the car running heaps rich, it gets 160rwkw at stock boost