When you installed the cold air kit, did you're truck have a small plastic "box" looking piece in the small hose from the idle air by-pass valve to the air inlet?? this is an air silencer to eliminate this noise. Cut the hose and re-install it, this will fix the noise. if you're truck did not originally have one buy one for a latter model truck, my 2001 came with one and when I installed my supercharger I had the same noise until I re installed it.

 

I have been trying to cut it in but i can't get it. I can't get it to all fit in that tight space and line up at the same time. A picture would be great.