High speed stability issues
Front of car is lifting, unloading suspension and altering toe?
That's a strong possibility. I have a street car that sails along at 120 all day long. But I spent many hours on the alignment rack fixing the toe pattern, and what-not.
As the suspension cycles up and down, because the UCA and LCA are different lengths, the camber HAS to change. And when the camber changes, the toe also HAS to change. With unequal arms it cannot be otherwise.
Your job is to just minimize it and then set your ride height in the best possible place to stabilize it at speed.
Your Scrub radius is another thing that can be affecting your steering at speed.
And of course the back of your car can steer as well, if one side or the other is growing or shrinking in length. This leads to a change in Thrust-Angle, which has to be compensated for, by the steering wheel. The wheelbase between sides has to always remain fixed, else, by definition, the car is turning.
