I was just wondering if you can hear the turbo spooling up pretty easy when shifting gears on the 04' STi? Just a dumb question, thanks.

I know I can her mine spool up in my WRX. Specially when I have the radio off and i'm cruising down the interstate. I give it some gas and I can hear it.

You can hear it, but it's pretty muffled. If you do the intake snorkel mod, or get an aftermarket intake, *then* you'll be able to hear it really clearly. A lot of people also state that they can hear the stock bypass valve with aftermarket intakes.