Your tires seem decent. They aren't tires that are used much on our cars that I've seen but probably not the main cause. My best guess is the surface of the road you are driving on. If you are going 120+ on a rough surfaced (public) road most people will experience some instability unless suspension, tire pressure etc. has been fine tuned. Please stop doing 120+ on public road if this be the case for your safety and others. Public roads were not constructed for high speeds.
On the other hand if you are experiencing instability on a very smooth track then it might be your tires or something off in your setup. It is kind of hard to pinpoint with so many variables involved. Anyone else got some input?