2001 Dodge Ram truck is making whistling noise when its col

My 01 Dodge Ram, 5.9L is making a whistle noise while driving, around 1600 rpms most consistantly. When I give it gas, it stops, when I let off the gas, it stops. Sometimes it will go away while driving in town, im guess when the engine bay area warms up. I've checked and taped all of the potentially bad vacuum lines that I can find, replaced the air intake gasket, changed the air intake completley, and have even taped up some evap system lines that looked cracked. Ive been battling this noise for a year, it happened last winter, and now this winter. And its annoying!