Can you have someone rev it while parked and listen yourself to isolate the source?

A mysterious "chirp" is hard to diagnose remotely!

 

I did something similar, I opened the hood and pulled on the throttle cable. It sounds more like a belt squeak, but it's not a consistent squeal and more of a chirp. However, I just did an emissions test and it was more of a consistent sound. Which makes me think it could be the belts.

 

Or just reach over and pull the throttle cable by hand behind the plenum. If it's super-hot, use a rag to keep from burning your fingers.

Easy test would be to remove the belts 1 at a time and drive around the block. It's less than 30 minutes to remove and put back on, but the PS belt can be annoying and need a helper from the top side.

EDIT: Posted at the exact same time as you.

 

I will try that. Thanks for your advice. I will post any updates.

 

When chirping noise is heard this could be a loose AC / Alternator belt
Check to see if they AC is running at higher rpm ..... making the belt squeal if AC is turned on

This could also very well be a harmonic balancer as well taking a doo doo ....

The OE balancer has a rubber bushing in between the pulley ring and the center base of the balancer as well
these tend to make noise when higher rpm is reached and having heavy restriction applied by AC compressor turning with the engine
Turning the crank pulley Harmonic Balancer making the pulley ring slip
Check this as well

 

The squeal happens with the AC on and off. I tightened the PS belt, but I haven't done the AC belt yet. When I installed the harmonic balancer it looked like it was in good condition.

 

I would double check it
Specially if your manual trans .....
Failure could lead to an over rev situation
Having some resistance on the crank and all of a sudden you don't

Snug up the AC / Alternator belt see if it cures this pesky chirp
Don't get to crazy tightening it up
Puts alot of wear and tare on your idler / tensioner pulley bearings
Will give off a roaring noise if it's to tight

 

I got a chance to look at the balancer, it looks like it's in good condition. I also did my first oil change, and the oil was very clean.

 

Here's a link to what the squeak sounds like: Mitsubishi 3000gt Engine Squeak

 

I think I figured out what the noise was coming from. I removed the AC/Alternator belt and the squeak went away. I reinstalled it with a looser tension than I had before and it hasn't started squeaking. Hopefully the belt being overtensioned was the issue, I will drive around for a few days to see if it really went away for good.

 

Take the accessory belts off and see if it stops.