SubieSmacks

I don't usually use forums but google is giving me general info not info for my car. So here I am. in case this is something to help yall to help me mods are my car is (Cool air intake, exhaust, tuned) Those mods are well over a few years old. I left the house. Car sounded and ran fine. 2 hours of driving later I hear a low whistle noise at around 1500 - 2000 RPM but no loss of power. No weird smells (other than the usual burning oil <_< trying to fix that as well) Is it the turbo, intake, exhaust? It's got 165K miles on it give or take.