I'm not sure how people have reverse engineered the injection logic for ICE cars, to get a boost of performance, but I would not expect a lot of hacks to come out anytime soon, because the "hack" market is going to be so small initially.
You still need to make changes, and recompile code that is compatible with all the other elements in the car, not easy without any source code. I would even argue that as more modules are integrated together (battery control , motor control, ac control, navigation), it makes it harder to hack one, compared to an ICE car where the module responsible for the injection doesn't need to know much about the tank capacity, or the AC setting.
Finally, you can't do everything in software. Batteries, battery management system, wires, inverter, motor have been designed for some specific current, and increasing that current may or not be possible with the current hardware. The same motor can come with different windings for example (you can trade torque for speed), while it may sound like you have the same power output, at full stop, the current draw will be very different. Change the mass / wheel size of the vehicle, and a faster electrical motor will be fine and won't draw too much current, but put it on a heavier vehicle, and you'll just melt the wires.
1st Leaf Order (order made and confirmed on 08/31 10:40am)
Delivered on December 11th 2010
15000 miles so far