Hello, I have a 2001 silverado z71 with the 5.3 engine and I have a strange noise while driving or during acceleration, the noise will stop when I let off the pedal and return as soon as I press the pedal again. The noise sounds like air sucking or maybe a heat shield rattling. I put the truck up on a lift and everything appears to tight, nothing loose or rattling including the muffler. The truck is all stock. Any ideas? Thanks in advance.