This is the reasons that BMW Asia gave on the voiding of the warranty :
Basically :
1) they are saying its perfect normal and nothing is wrong and that the DME showed nothing out of the norm.
2) The spark plug was replaced with the same OEM NGK R spark plugs because I had the misfire. It is really quite amazing that they do not trust customers to change the plugs outside BMW??? I had to change my spark plugs outside because the track event was in Malaysia which was 340km away. I had to drive my car back to Singapore and needed to get my plugs changed at the nearest workshop. It was as simple as getting the plugs and getting the workshop to replace it. Nothing to do with rocket science.
3) The most absurd comment ever. The sound came from the airconditioner and that it was the cause of the sound. The sound has always been there since the misfire and it is clearly audible.
4) Pretty self explanatory.