06 chevy silverado, stereo wiring

What harness are you using? Those vehicles don't have a switched power source at the factory radio. They have a system called class II data bus. There are data signals that are decoded by the radio to turn it on and off. Either you need to run a new wire to a switched source, or use a harness that can integrate the Class II system.

I would recommend using an inegrator harness. There are some other features tied into this system that you will lose without this harness such as the door chime. Not to mention its less work for you to do.