So had the car 6 weeks and it’s going in for its first 1000 miles service. Someone at BMW told me that once this is done, the power increases from the engine as there is a limiter up until this point. Is this true?
No, what they probably mean is if you have been following the RIP you won't have experienced full power at WOT and max revs, therefore you'll be able to use full power rather than the engine having some sort of software restriction prior to the RIS.
