Sounds like my 02 Blazer has a supercharger but definitely doesn’t
 

My blazer (LS 2002 2WD 4.3 vortec) sounds like it’s supercharged whenever I get to high rpms. Any ideas??

Clogged air filter, or air getting into the intake tubing somewhere it's not suppose to?

How high of RPMs are we talking about here? How loud is the sound? Any chance you could post a video?

i just changed the air filter and it’s still making the Noise, it gets you about 4000rpm and that’s when it gets loud enough to really hear it. Let me see if I can post a video and get a link for it

Sounds like belt and fan singing - imo sounds pretty much normal for just revving the heck out of the engine sitting in park/neutral ....

Honestly to me, that sounds like alternator wine.

well it does it while driving too even when I don’t go super high rpms it’s just louder the higher rpms it gets

so then I’m guessing I shouldn’t worry about it?

I had the same thing in my 99 blazer it was the idler pulley bearing. You can get a new pulley from advance auto for 20. And it takes 10 min to swap. When I took the old pulley off you could definitely feel the roughness when spun it

I would recommend you pull the belt off and spin your pulleys. Check for any growl or play. Can get some pretty strange noises from those guys.

It could be a bad Fan clutch. Rent a 36 mm wrench and you can take it off and the 4 bolts that hold the hub on. Check the fan clutch first.