I believe all F8x cars are limited to 275 kph. Unless they have the driver's package code (downloaded at a dealer, once you go thru a BMW driver's school) to up the V-max.
IF you account for a 5% speedo(over correction error) this 291 kph is really 276 kph(GPS). Just what BMW limits the cars to.
A friend of mine has coded his M4 to a 320 V-max... but so far he has not found an empty enough autobahn to "test" his new V-max.