paul mate i know your a knowledgable dude, but it still very well could be turbo seals :harhar: as said yes it points towards h/g failure but my point is that the smoke never happened until a while after replacing the belt if the h/g went immediately due to the snapped belt he would most likely have had the smoke from then on in (especially if he was to have warped the head) but never, took a couple of weeks so what i would do and still stick by is do a co2 test that way you know for a definite but i know it is more likely a h/g failure, but doing a co2 test saves ripping the head off to find that it was not the h/g .