when you are adjusting the expo for throttle, use the adjustments in the esc. Sometimes you can't, but if your esc can, do it that way, it works much better.
As for steering expo, it can help reduce the twitchy feeling, but adding toe in (1/2 deg or less) works better and compromises the handling and response of the car less. Also, try turning your dual rate down and learn to drive using smaller inputs instead, with the wheels turning less, you will carry more corner speed.