And to complete the picture, I cannot fault my G56 with their own ECU, fettled perfectly by the very helpful Dan @Krazy Horse. So much smoother and more responsive than stock and although I've not driven an MMC-S1 car, nothing makes me think I'm missing that 'factory' something.
I'm also with Headley and they were perfectly happy with the update. I suspect there's no such thing as a standard M3W anymore - not even those that leave the factory doors - as they all break in one way or another and are fixed with a range of differing solutions.....
