It all depends on what is done to the car, and how well you tune it. Horsepower isn't the only thing that will make the car go fast. 10-15 hp if you do it right, I suppose. For those who are only going to get a few mods, I would suggest PCMforless tune your car, or have it dynotuned, as like evilkal said, it is a little more complicated than a handheld. Handheld tuners are in my (and many others) eye, junk.