Hello, I have a 2001 z71 extra cab and I have a strange noise while driving. The noise sounds like air sucking or maybe a loose exhaust heat shield. The noise will stop when you take your foot off the accelerator pedal and return as soon as you press the accelerator. The noise only appears while driving, not while sitting still in park or neutral. The truck is all original and i had it up on a lift and everything is tight with nothing loose or rattling that I could find, also with no codes or check engine lights. Any ideas? Thanks in advance.