Ok, I have a 2008 Clubman non S with 67k miles on it. Yesterday, I replaced the front parking light bulbs, filled the gas tank and topped off the oil with Castrol 5w-30 Extended Performance Edge. Today, my Mini has a stumble at idle. The only mod I made was to install a K&N air filter.

It is a non-S and ran great until yesterday. I suspect the plugs or fuel filter. I did fill up with some independent brand mid-grade in Lake Tahoe.

I changed the air filter about two weeks ago and was very careful. Since then, I have driven to Lake Tahoe and back without a problem. I am thinking that when I filled up in Tahoe, I got some sketchy gas and the top off stirred up some dirt from the tank and the fuel filter needs to be changed.