Faint, high-pitched whistling sound
 

Anyone else having this issue?

• 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

You nailed everything I thought of at first.
Vacuum leak someplace?

If there is one, it would affect my MPG somewhat, and I'm still in the 23-26 range. Exhaust still sounds normal.

If it was bad enough that it effected your mileage you would throw a CEL.
Have had that sort of sound you described from collapsed vacuum lines or very small holes that didn't impact the actual system before in other cars. They are an absolute bitch to track down!

http://www.ft86club.com/forums/showt...light=vac+leak

This hose is still attached properly, as far as I can see.

I'm assuming that this occurs while driving?

Yes.

> Cannot reproduce if the car is parked and I rev

Chance that is a wind noise through the grill or from around a headlight or turn signal?

That matches the RPM?

So you're only hearing it at a specific RPM range in each gear and not once you reach a certain speed?

Nope, across all range regardless of speed, but the car has to be moving, which is so weird. It gets subtly louder with increasing RPM.

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

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 ...........

Alright, let me try this later on the way home. Good call.