Before spending $$$ on a steering stabilizer, you may want to look into some maint and setup as mentioned above. Under normal conditions, an SV shouldn't headshake. While a steering stabilizer might keep this from happening, you're just covering up a problem, not solving it. You might want to check your sag, and make sure the rear isn't too soft. If it's squating under accelleration and unloading the front, it could cause a headshake to happen when you shift (you're unloading the rear and loading the front for a couple seconds).