getting a throbbing noise and feel through steering when turning only.

Hello, inspect the steering gear for leakage, and let me know if there is play in the steering column/steering wheel before the vehicle begins to turn. You may have a worn worm gear that is binding and causing the power steering pump to make noise. Also, the power steering pump can be tested with a pressure gauge in the high-side line. If you need further assistance, let me know, otherwise, here is a list of certified shops in your area and repair your vehicle: http://repairpal.com/chevrolet-within-10-miles-of-pinon-hills-california-92372