2006 STS rotors

Rotor concerns may not be caused by faulty parts. It sounds like you may have addressed this concern more than once. First question is, is the vehicle in factory state, no modifications? Are you the only driver, or is there others? Where are you having the repairs performed? The reason I ask these questions is this. Brake pulsation can be reocurring due to substandard parts, but that is not always the case. Simple procedures at brake service can make a difference, as well as driving habits. If you had factory replacement parts, done by service personnel that cleans hub surfaces, resurfaces rotors on-car, and torques wheel bolts, all is being done that can be done. Driving habits, or improper service procedures, can make pulsation reappear more frequently.