I really don't know, so many ideas have been getting thrown around that i'm just lost. Can't keep up this trial and error stuff though.
Just to add, it has been doing it when putting my foot down sometimes or if I go round a corner quite hard. But mostly when i stop start in traffic, it leaves a BIG cloud behind me, also noticed it if i am going down hill in gear but not accelerating. Not sure if any of that helps diagnose at all.