[Nathan]

That is the full story- More current, more tourqe. More tourqe, more speed.

Simply unwinding your stock wire will decrease tourque and increase speed. Replacing it with a smaller gauge (bigger diameter) will increase tourqe and speed, but your batteries and PCB can only flow so much current, which is why tourqe drops. Inductance also affects the tourqe-speed balance, and windings effect inductance. That's why some 1/10 motors have multiple winds (10T double, triple, etc.), to alter the inductance, decreasing tourqe for more speed. Better magnets are usually a plus, different winds can negate the speed loss. 1/10 motors just use insanly strong magnets, especially for "punchy" applications such as touring cars.

Of course, the size of the motor limits your winding options as nuero pointed out. If you could wind one with 10T of 8G wire, and had the current to do so, it would be faster and tourqier, as well as draw huge amounts of current.