Originally Posted by P3Auto
If you took the oil cap off while the engine is running then yes there is crank case pressures. This is normal and this is why there are 3 or more crank case and valve cover vents.
The loud whistle could be a lot of things. Turbo going bad, air filter issue, boost leak, etc.
I doubt it is related to the oil cap unless you left off or forgot the rubber oring around the cap, even that would not cause and loud whistle I think.
No, I let the engine cool down before i took off the cap, I took it to my local subaru dealership and they said it was a leak but have been unable to find it so far.