Stock plastic turbo inlets have baffles and what not that quiets it down a lot. My T3 with an open pipe is wicked loud. I also have an open 2.5 inch exhaust.

 

What do you mean by open pipe?
On the intake side or exhaust side?

 

my friend bought an srt-4...had the stock intake on it and he put an injen intake on it...now u can hear that thing a block away...try doing an intake

 

I have plastic intake arm and one of those cheap ebay HKS style filter with 2.5" exhaust and no cat. Sucker spools like a one of those damn semi trucks... maybe not that loud but you can hear me quite a distance away.

 

The K&N Typhoon is extremely popular with the Sti's and it will make the BOV much louder, but everyone says that the sound of the turbo is no louder.
I can't figure out what would be making it so quiet

 

it has to do with the turbo size and exhaust setup. a smallet turbo likea vj-11 will make more sound sooner than a t3.. simply because its spinning faster.. most turbos operate in acess of 150,000 rpm.

 

I believe you that it does have to do with the size and exhaust(as well as intake) setup, but the second half of your statement is kind of pointless to be frank...

 

if he wants to feel smart and tell all the turbo guys how fast turbo's really spin..then let him lol

 

ive been wondering the same thing, my friends t3 .48/.42 with a open downpipe is ------ loud, nice wistle to it.

 

mine is pretty loud. 3 inch dp with 2.5 exhaust thru a magnaflow muffler. its almost annoying. i have a U shaped intake on it with filter as well, tapped with a fitting for my PCV setup