I am having the older version of the RS4-3
Nothing too special added on it.
Apart from the HD diff gear ,HD pinion and HD outdrive everything is much left stock.

Meantime I am running an old Kyosho Super Ten pipe. (the one in red colour). Power band is a lot better as compared to the composite tuned pipe.

I also changed to the clutch type 2 speed after my finger style 2 speed tranny gave way.
I really like running this car and handling is very neutral and really hard to swap ends. (which is a good thing)

Oh yes, you have to get some pinions and spurs if you are running in a medium to large track.. The standard gearing is too low.. I am running 41-37 with 18-22.. Seems fine for my track...