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Have you guys, with the problem, established if it a wheel size, even wheel style related issue? Some early posts were trying to establish if it is wheel (more than simply tyre) related.
Reading through the topic, I'm not seeing that wheels have been eliminated, when it is clear some have a different sound levels on different surfaces, that does indicate wheels are involved in some way.
Depends what is generating and/or amplifying the sound, and what route it is transmitted to the cabin. Is the transmission air-borne, or has it a structural path? Even if it is not the tyres, it does appear the sound generated from different surfaces (changing levels) does get involved with the resulting sound track.
M-sport dominance (different suspension frequency) indicates a structural transmission to the cabin, hence why wheel bearings have been suspect and changed. Many wheel bearings are declared a problem with noise problems, when it is nothing to do with the problem, a wheel/tyre generated noise often mimics a bad bearing sound.
From an outsider's perspective, trouble shooting is the hardest thing to do with problems like this. 'Hands on' is the only way I've ever solved difficult problems in the past, when I was in the trade. You have to think laterally. Is it something simple like a wheel arch liner, or a heat shield, free to resonate with the wheels and/or air flows as speed builds up? Or simply stressed some way and acts like loud speaker, transmitting the sound to the body. Adjust or 'damp' the component and no amplification takes place.
Similar issues happen with engine acoustic covers, if they are not fitted correctly (or stressed), can generate some pretty strange engine notes and vibrations at specific rpms.
Following this topic with interest, now that I've read it through.
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