I have had my car on Summit and on Watkins Glen and every instructor I've had has commented on how stable the car is at speed. It might have to do with driving technique/ability it might be that you don't really do emergency lane changes while on a racetrack (hopefully).
If you want to get more stability and are taking the car to the track then I'd suggest the following upgrades:
4. Better shocks/springs
3. Better tires.
2. Better brake pads/fluid.
1. Improved input nut.
I'm not saying that to be an ass and I'm not saying you don't know how to drive. I'm only saying the best performance upgrade you can do for your car is getting better at driving.
