Whatever you do, don't add 3" pipe, a big ass wing, and a fart can to the volt - that won't help. As sharkvolt said, smaller diameter wheels and tires will help with acceleration, but your top speed will suffer. You also have to reduce the weight of the overall package, or else you might not gain any ground. Plus the lower you go, the more of a chance you'd do some major damage with potholes and such.
Rather than jettisoning the spare tire in the hatch, a good fitness program might help get rid of the spare tire on the average American torso. Some crazy folks would tear out the seats, carpeting, headliner, door panels, anything in the name of saving weight.
But my best advice is to save your pennies to get a Tesla with ludicrous mode. You only need about 9 million of them, or convince 90000 people to give you 100 pennies at a time. A less expensive technique along this line is to get a used ELR. The ELR will actually use the battery and the ICE together for faster 0-60 times in sport mode. Plus the car is such a sexy supermodel that you'd be willing to risk your marriage for a ride. Now if someone could fool the volt into thinking it was an ELR, that would be something. It's the same basic engine/twin electric motor setup with different software.