Scotty, the S button does not change the fuel map. The only thing that the "S" button does is open the valves at the muffler exit ports and quickens the throttle response.
For those who don't think that they can feel a difference when the "S" button is engaged, put the car in first gear and let the car roll while it idles, then tap on the gas a little. When the "S" button is off the car is real smooth. When the "S" button is activated, the car will jump and it will be harder to modulate the rpms, car, gas pedal. Other than this scenario, it's really hard to tell a difference.
Last but not least, it's accelerate. Sorry, I had to go there!