Without actually seeing the whole package it is all speculation.
If we go back to a drag car there are a lot of things that need fixing beside the motor, first you get the motor to a middle stage then work on suspension, gearing etc. Then go back to the motor and do the whole cycle again.
Leg speed can be improved(horsepower), strength(torque), gearing(stride length) balance(suspension).
A balance needs to be worked out between strength and leg speed, without proper balance the stride length is shot to pieces and the whole exercise gets frustrating.