Make sure you are not in the Suspension settings. On my car the Sport is very firm, and I prefer it. There are the same settings in Suspension, but they do not affect steering effort.
Adjusting Steering Effort
You can adjust the feel and sensitivity of the
steering system to suit your personal
preference:
1. On the touchscreen, touch Controls >
Driving > Steering Mode.
2. Choose a steering option:
• Comfort - Reduces the effort required
to turn the wheel. In town, Model S
feels easier to drive and park.
• Standard - Tesla believes that this
setting offers the best handling and
response in all conditions.
• Sport - Increases the effort required
to turn the wheel. When driving at
higher speeds, Model S feels more
responsive.
The only way to really know which option you
like best is to try them.