Another thing to bear in mind with the 3Racing diff is that the standard o-ring seals are exceptionally stiff and cause a lot of drag. I'd run-in the diff for as long as possible to bed them in before choosing the oil and putting it in the car.

I've got a feeling I had to remove some flashing from the circumference of the gears, but I am running the full complement of shims in mine. Since each moulding is slightly different, adding or removing shims can help.