I have a 2011 WRX TP stage 2. Stage 1 was fine with no issues; but when I went stage 2, this noise came up. It is pretty loud, I thought it was an exhaust leak at first. After replacing all gaskets and checking all connections, the exhaust is sealed up.
The sound is like a sewing machine, and coming from the drivers side of the motor. When I drive at low speeds, you can hear it loudly when it echos off of passing cars. No loss it power and datalogs look fine. There is a bit of knock up top, but the tune is still being worked on.
I have a video of it, but I can not figure out how to upload it..