My '01 did the same thing..
Like a mouse in the engine...injectors...
My 07 Tahoe has recently been making a high pitched squealing sound at low speeds. Once underway ~30 mph, the noise goes away. The noise sounds like it is coming from the engine bay.
I have ~500 miles on the truck with no mods to the engine. It seems like a few people are experiencing this and hopefully the person getting their truck inspected can update us.
Like a mouse in the engine...injectors...