The OP is asking for help on an issue the vehicle has, that he picked up when doing excessive speeds on what I presume to be a long, straight road with barely any traffic on. We have all pushed our cars to (or near to) the limit when given an opportunity to do so, such as on long open roads on your way down to the coast. He has not mentioned illegal racing or that he was doing it on the N1 in peak traffic times. He owns a vehicle that was built to do those excessive speeds, wherever it may be, and now states that the vehicle is not performing as it should and would like to resolve the issue. Perhaps this was his first time doing that speed for the thrill of seeing what his car was capable of?
Would you help him better if he said he picked up on the problems at those speeds whilst doing a 1km run at ODI?
Now, I am in no way promoting the activities of the OP, and I do not condone street racing or reckless driving. Let me state here and now that BMWFanatics and TheFanatics does not condone illegal activities on the roads in any manner or form whatsoever, and that the forum supports the Arrive Alive campaign.
That being said, it is perfectly understandable to see where the OP and his concern is coming from. Would you be happy with a car that doesn't perform to the best of its capability? This is ultimately the purpose of this thread.
Please offer him the knowledgeable assistance I know this forum and its fanatics can offer, which is what he came here for, rather than berate him on what speed he was doing.