what truck? i put it in my revo 3.3 and it made it accelarate better it takes out a bunch of gears from the tranny the servo,opptidrive unit. less rotational weight in tranny= faster.
yes FOC is a good hop up,it saves you some weight but also energy needed to move truck and micro servo would be not needed any more...
so in fact you are throwing away a lot's of parts that will save you weight...