Ok, well I have about 37k on my 03 evo and have every bolt on imaginable(alky, intake, tbe, etc...) and yesterday for the first time I hear this air sucking noise from my engine bay. It only happens when I am in vacuum(at least thats when its noticeable) and once I get into boost, I cant hear it anymore. I thought it was the xfer case, but I am not sure what exactly the sound a bad xfer case makes. My next guess would be a blown/loose coupler. Id check now, but I am at work. Anyone have ANY ideas before I get into it? Thanks in advance!

 

hmm...I get this sound too.
I was just assuming it's normal since I have a tbe.

I"ve checked all the clamps and they are on tight.

Let me know if you find out what it is.

 

At idle is the DV opening to let air back into the intake. Under boost - thats the turbo. Do you have an open element filter? I know you know the difference. Check the turbo inlet clamp too (the post MAF to inlet one).

TCs make a loud whining noise all the time when they are going/gone.

 

It almost sounds like a leak, but I havent really looked yet. I will be off work tomorrow so Ill find out in the morning. Its not the filter, lol.

 

leak. Find and plug it

 

hahaha, I hope so!