It's not carbon build up...
I have the indentical issue, idle shakes and shivers followed by the idle speed rising from 600 to 700rpm.
I've had new plugs, injectors, coils, full decarb, adaptation resets, vanos solanoids the list goes on and still no fix.
As its only a problem at idle i've just accepted it and moved, maybe one day one of us will find the anwser.
