So I've had a similar experience had the noise, then rotors, pads etc changed at around 4000k's noise came back within 2000ks I gave it a few months to settle , no real difference im at now 7800k's with the replaced parts so 3000k's in and its still there, more so Id when the pads are hot it'll do it, so went in to my local bm d/s where I purchased the car from had a conversation, which basically went like this mate I think its pointless replacing rotors and pads every 3000k's , its a waste of your time and my time , I'd rather a proper fix and not a band aid fix, so we've raised a case direct to BM with video attached and see what happens. But at this point Im not too fussed as I think ill end up traded and making a move on the new M2 or a low k's F87 M2, once their on able to be ordered here in Australia, other then that it's been faultless.