Isn't it amazing how many people on this section of Yahoo Answers that have bought little 4 banger economy cars and are not satisfied with their performance.
They don't realize that an internal combustion must burn fuel to make power. The more power the engine makes, the more fuel is required. So if you start souping up these little 4 bangers you lose your fuel economy.
Also, when you start souping up these little 4 bangers you risk losing your reliability.
If you want better performance, sell your little 4 banger economy car. Use the money from the sale to buy something with a larger engine that makes more power. You will have a vehicle that will perform better along with reliability and take less of a hit on fuel economy.
In the long run this will give you the best bang for the buck.