When I accelerate, mainly aggressively, I hear a very faint-but-noticeable high pitched noise coming from under my hood. I use regular fuel, so I have no idea what it could be. Any ideas?

 

oh and its a 97 ES300

 

Do you have an aftermarket stereo?

 

Nope. Stock Premium Sound System

 

Try revving the engine in park. Open the hood and use the butterfly valve inside the engine bay to do it. If you hear the noise, you'll know it's coming from the engine. If not, it could be coming from the transmission and/or wheels.