Idle Vibration/Rev Issue

[OBOB]

Hi guys, I have been having an issue with my 2026 with 5100 miles, it has a slight RPM fluctuations and cabin vibration at idle, mostly when cold but occasionally warm. The car will make an different audible engine sound, rpms will jiggle and there will be a shake through the cabin. Car was bought brand new, followed break in procedure, only has a catback, and is running 5w30 bmw LL oil. The Toyota found no misfires, and BimmerLink shows no fault codes. Is this normal, or would you recommend checking anything? Car seems to have gotten this after installing catback or changing oil but I do not see how that could affect the powertrain so much. Thank you for your time and help!

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My Z4 does this as well, as did my 135i before it. I've gotten to think BMW engines just don't have a smooth idle.

My X3 is pretty good though, but it's an automatic (the others are / were stick), and I wonder if that makes a difference.

Curious if others have knowledge about it, but until then as a random data point, I've got similar fluctuations and always have.