Sale Killed by A Noise - Know Your Noises

I had a guy drive all the way from AZ to ID to buy this truck, but he changed his mind after driving it because it was making a new noise. I tried to tell him it sounded like an exhaust leak, but he was unsure so he headed home without the truck.
So, what was that noise? I tore into the truck this morning and fixed it. I'll show you what I found.