Started immediately on first drive home with the car, and has been there ever since. Whenever cruising along and the car is in 6th gear (even at City speeds of 50 km/h, but also at highway cruising speeds), car is at about 1k RPM, and there's a low rumble/vibration... best feel I can liken it to would be trying to start a manual car off the line in 4th gear. Slight tap on the gas, raises the RPM's to about 1500, and the rumble noise/feel goes away.

Could this be related to the car going into 4 Cylinder Mode? Anyone else experiencing this, or have any suggestions? I'm going to be taking it back to the dealer service center on Tuesday (one wheel's out of balance, there's no weights on it at all - not sure how that got missed), but I'd love to have some kind of idea to lead them on about the noise/feel I get.

Any help appreciated!

Thanks,
Yaladorn

it's the AFM dropping the engine to 4 banger mode...nothing to worry about. i got used to the slight rumble/vibration fairly quickly...

What he ^^^ said AFM (4 cylinder) mode...

AFM dude no need for service, its a good thing lol

Thanks folks, much appreciated!

Try higher octane, I noticed my AFM makes more noise with 87 and is a lot smoother and quieter with 93.