[DCleghorn]

Just recently I started having a strange noise coming from the passenger side of my engine bay Since I've got the noise, my car has had a really rough startup and idle.

When I fully stop after driving, the car hums very loud for a couple seconds then quickly stops to a low hum. I've also noticed that the car has been struggling more once I get up to around 130km/h.

I replaced the PCV about 30,000 ago so I'm leaning more towards the Cats, however I'm not getting any codes when I scan and I've never got a check engine light.

Here's a video:

Any helps appreciated, it's a 2011 328i Xdrive with 165,000 on it.