I drive a MCS 2008. So I just came back from a 15 min car ride then while dropping a friend off i left it idling for 10 mins. When I set off about 20 feet my car starting doing this. I cant rev it pass 3k. I was thinking it might be a mass air flow sensor or the oxygen sensor. It just hunts up and down. And when i drive its really slow

 

Mine was doing that but not as drastic.....after a fresh oil change, everything is normal again.

 

Could be your high pressure fuel pump. No point in guessing as the car should have a code stored from the check engine light.

 

The code are P1497
P0507 idle control system rpm higher than usual
P1638 Throttle Valve Adaptation Control, Throttle stuck temporarily
P1637 Throttle Valve Adaptation Control, Control Deviation

 

Whats the temperature in your area? The car could be failing its drive by wire calibration at start up. My car also had the intake manifold revised from the original piece that was fitted because the original design allowed water from condensation to build up at the throttle plate which would cause it to freeze stuck in postion. Those codes suggest that.

 

The problem is that it only happens when the car is fully warmed up. I live in Nor Cal so its not that cold. Im thinking it might be a vacuum leak but im still looking.

 

Typically stuff like this is just a vacuum leak. You can take it to a shop and have a smoke test done. That's probably the easiest option. Sure beats trying to hunt down a vacuum leak yourself.

 

Mine threw P1637 and P1638 yesterday when I started it to go home from work. It was approximately 3 degrees here yesterday afternoon. After shutting down and restarting twice, the third time was the charm. Idle was normal after that, and it drove fine all the way home. I suspect condensation to be the culprit in my case.
What is the revised intake manifold design? Did you have this installed by Mini?

 

Mine also has done this after an oil change, that when it first started. It was going from 800 rpms-900 rpms just like the OP's video and it wasn't cold.

I never get codes, even when the craziest crap happens, like starting your car and having it race to 6000 rpms for a few seconds with zero throttle input! Only happened once almost a year ago, oh yeah no code was stored. The only time I got a "Check Engine" light is when I installed my MAF sensor backwards. Don't ask.

 

ACTE,

I had both the 1497 and 0507 codes a few months back. It was a valve cover leak. I popped a 1638/1639 code on really cold days (-10 to -20) but after warming up and restarting the engine, it clears itself.