My 2002 WRX has 126K miles on it, but the motor was replaced at 84k (short block).
My mods include a GFB Stealth BOV (came with the car), a Mishimoto radiator, and Stage 1 AccessPORT tune.
My car started leaking a little oil a while ago, so I took it to the local Scooby dealer. They replaced the head gaskets, and said that all else was fine. Right after I got the car back, I noticed that the car was making a funny noise under boost.
The noise happens with anything greater than 30% throttle, and only after the boost guage is above -0.02 MPa.
I watched a bunch of boost leak videos on youtube, and the noise is low-pitched compared to that. It sounds as if the sound of the spooling turbo has been amplified 5 times. It is like a banshee screaming with a gurgle, or Rales for the medical people. I put the old bypass valve back on the car with a new gasket, and the noise didn't change. All of my vacuum lines are fine, and all connections on the cold side of the turbo are fine. I took the heat shield off, and there was a little bit of black residue on the inside/back flange, at about 9 o'clock if you are looking at the front of it.
The car is still boosting fine, and there is no loss in power. The gas mileage hasn't changed either. I always run 93 octane, and replace the oil with Subaru synthetic every 3000 miles.
I know it isn't rod knock, and the compression was just checked due to a bad fuel filter/misfire code. There aren't any codes being thrown at this point.
Could it be a leak on the hot side of the turbo (UP/DP exhaust leak)? Any other ideas?
Thanks in advance for any help.