I am 99.99999999999999999999999999999999999999999999999 999999999 percent sure that it's your turbo.

 

If it is a whirring sound, it is probably your transfercase or transmission spinning down. Evos have a lot of drivetrain noise.

 

I'll have to go with ZK on this one. Transmissions whine at lower speeds (all the time coming into stoplights in 1st/2nd gear)

If your car is parked and is making the noise, it isn't the tranny.

Ask around. Someone will know what it is, probably laugh at you and tell you its nothing to worry about. But at least you'll know. Good luck