My SC430 and IS300 both had an ECU that adapted to how I drove, which mostly meant that the car adapted to how I touched both pedals. I'm assuming the GS has the same technology as my older cars. If you think it's too sensitive, the car will eventually notice you touching the gas then pulling your foot off and then touching it again. It will then lower its response until you always smoothly touch it.
If the car didn't respond enough, it would notice that when you push on the gas for a moment you then push harder, and eventually it'll respond more aggressively to applying pressure. It will reach an equilibrium at which point when you add gas it'll accelerate at the amount you like without the need to push harder and harder, or needing to jerk your foot off the gas because it gave you too much.
The long and short is, the car is just too sensitive for you, but over time it will restrict it's actions to match your driving style.