Sometimes at idle, i hear this clunking sound that sounds like it's coming from the gas tank, almost like it's being sucked into itself. This noise also often happens when I open the gas tank.

Lastly, It seems something is squeeking when it rains, or if the truck has been sitting. The squeek i've concured is either the belt or a pulley, how do i tell which it is, and being the belt is only a year old, it's probably a pulley, how do I stop them from squeeking?

 

Sounds like the gas cap is bad .
Try running it with the cap off to see if there is any noise.
Been there done that, Squeekey belts SUCK. I tried different belts also, no luck ended up changing the waterpump pulley
never had another problem since.

Hope this helps
Bob