Faint, high-pitched whistling sound

[ls1ac]

Do as suggested and while it is happening put the car in N or depress the clutch, if it decreases or goes away it is engine related, if it stays it is drivetrain or body.
Revving the engine standing still produces very little sustainable manifold vacuum. You may still be able to find a leak using brake cleaner and listening for a RPM change while at idle.

[retrosmiths]

Originally Posted by ls1ac

Do as suggested and while it is happening put the car in N or depress the clutch, if it decreases or goes away it is engine related, if it stays it is drivetrain or body.
Revving the engine standing still produces very little sustainable manifold vacuum. You may still be able to find a leak using brake cleaner and listening for a RPM change while at idle.

Originally Posted by White64Goat

That would tend to eliminate the throw-out bearing (if it's a manual trans.) Since you only hear it while moving my next thought would be a dust shield rubbing on a brake rotor.

What Shutter said ...........

Originally Posted by Shutter

get up to speed and throw the car in neutral? Just to make sure its not a wind noise from airflow

determines if its from the engine, or car

Ok, this is weird. Now I hear it while revving even when the car is parked. It's also near the passenger footwell, which leads me to believe it has something to do with that noise generator pipe, or something beneath the chassis (i.e. exhaust pipe).

The engine also needs to be running for quite a few minutes (10+) before it starts happening, like a certain temperature. Could it possibly be a small leak in the exhaust pipe, which only opens up when the temperature is high enough and the metal expands/contracts?

[Tcoat]

Originally Posted by retrosmiths

. Could it possibly be a small leak in the exhaust pipe, which only opens up when the temperature is high enough and the metal expands/contracts?

Yep!

[cdrazic93]

First thing that popped into my head was trans related. But it doesnt whistle.

My money is on a ever so slightly warped gasket near the sound tube.

[Jesse36m3]

SO weird. I've been having this problem at highway speeds. Exactly as you described. At first I thought it was a ground loop issue with the stereo, but I shut it off and it still remained. My car is also 100% stock.

[retrosmiths]

Originally Posted by cdrazic93

First thing that popped into my head was trans related. But it doesnt whistle.

My money is on a ever so slightly warped gasket near the sound tube.

Was planning on getting an inlet tube, hoping that will fix this.

[TheyCallMeBaker]

With your "symptoms"

"Usually happens when the engine is warm
Gets a bit louder/higher-pitched on higher RPMs
(NOT!) Cannot reproduce if the car is parked and I rev
Sounds something like a tea kettle noise
Stock exhaust pipes, stock intake system except for K&N drop-in filter
I triple-checked the filter to make sure it sits properly and that the box closes fully
I also plugged the pipe that leads from the intake to the cabin, and it didn't help
No matching symptoms with an intake/exhaust leak

First thing I'd do is get your hands on a back pressure gauge that you can put in your O2 sensor before the cat. Do it cold then let it idle and get to operating temp. Check where gauge is, roughly 4-6 psi is acceptable. If it's higher or pegging the needle and fluctuating I would replace your catalytic converter. Too much back pressure can leak out of gaskets causing your symptoms. Just personal experiences. I work in a shop not saying I'm 100% sure but I've seen it often on other vehicles. Havnt seen a case on a frs or brz but it could happen. And in my frs I've put 22k on it back roads and a few canyon runs but never had 23-26 mpg I'm sitting around 29-31 with k&n also so it could be I drive like a grandma but I'm leaning personally towards a cat.

[pdhami]

I literally just had the same problem as you on my drive to school and then on my drive home the sound is gone, I hope it doesn't come back it scared the shit outtve me when it happened haha

[orangeblue]

I've got the same thing, it happens at freeway speeds while feathering the gas. No throttle and the noise goes away. I drive 60 miles a day (at least) on the highway, so it's annoying.

[retrosmiths]

It sounds like a whistle, at the same time it goes up in pitch the higher the rev is.

[White64Goat]

Well, has anyone found the source yet?

[unlimited86]

I just notice mines today, Only happens when I am in 6th gear and at least 3k rpm, it gets louder when i get it up to 3.5k and the sound will go away if i let off throttle and will come right back when Im on it. Does not happen in other gears and I would say its more of a whining sound, its going to be irritating going on long road trips.

[Wyattkb]

I have this same thing, very noticeable at 75+ MPH. It sounds to me like some sort of gear whine.

[unlimited86]

Originally Posted by Wyattkb

I have this same thing, very noticeable at 75+ MPH. It sounds to me like some sort of gear whine.

Yup, exactly. Don't have any aftermarket parts that would increase NVH.