Okay, I am going to try to explain this as best as i can. I have an 03 WRX 110,000 miles, turbo back exhaust and k&n intake. Just recently ive been driving it and out of no where i hear a hollow whistling noise ...almost like your blowing into an empty glass bottle but a little bit higher pitched. It will stop after awhile for no apparent reason and when it is doing it everytime i even remotely hit the brakes it stops but when i let off it starts doing it again and it will eventually stop all together. I am completely baffled by what it would be and was wondering if someone could possibly point me in the right direction. I also am not sure where to post this so if its the wrong section, sorry. Any input would be good.