2004 Mazda 6.
My friend and i were messing around at lunch and revving our engines. My mazda was in neutral and i revved up annd after i let off the gas it made this crazy loud squealing noise. like way loud. only as if revved down though. then it stopped.
it has done this before. Like when i gun it onto the highway it will revv up and stuff, then as i let off the gas it squeals.
its not a belt or anything cause its not constant. only while its revving down the rpms after accelerating.
it doesnt do this every time i gun it. But it does only do it when i gun it to really high rpms.

sounds really bad. my friend mentioned a flywheel. im not really sure what to do with that.

it has 106,000 miles.