Just went though and got some, you can start hearing it at around 20 seconds.

It kind of sounds like a vibration but I'm not to sure...

It was recorded from the little windscreen wiper shelf in the middle.
Weird engine noise - 2006 WRX - YouTube

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2006 CS9 tuned to 225.6HP at all four
2004 MV Agusta Brutale 750