I have a 1999 K1500 Suburban with the 5.7 vortec. Lately it has developed a whistle, almost like a flute sound, that is coming from where the fuel lines enter/exit the upper plenum. It starts within a few minutes after starting the engine and will not stop until the engine is shut down. The only time it does not happen is when the outside temperature approaches 0. The truck runs great with no other symptons. Replacing the fuel filter was of no help. Any ideas?
Thanks, Bob