Still need to know part number for the harness. And if your truck was originally equipped with onstar and Bose

Here are a few things you can review right now

-grounding, check all your grounded connections, how is your amplifier grounded? Grounded to a seat bolt is not good enough, drill a small hole in your floor and bolt the ground right to your truck body

-second, instead of running your power for your deck off your harness, run 2 runs of 12awg from your amp to your deck (run 1 to your hot and 1 to your ground). This gives your signal output and input common power and ground, on big systems this is how we power our decks. It helps eliminate white noise or static sound of any kind (mostly known as pink noise)

-last thing, you may need to go to an audio shop and by what's called a ground-loop-isolator. This is another way to eliminate noise.