Yes, after much to-ing and fro-ing with Gates support, I've concluded that it's best to replace the tensioner pulley and other pulley on the old backplate with the new ones that come with the new backplate, and leave the old backplate in place. This is NOT what Gates advised, which was to replace the old backplate with its old pulley with the new one and its new pulleys, even though the pulley spacings on it are different.
As several people have said it's not strictly necessary to bother with the white & yellow markings on the belt. However, Gates advised that the use of white or yellow markings depends upon the position of the OTHER pulley (the one immediately up from the crankshaft in an anti-clockwise direction). For earlier engines (up to 1999, with the pulley in a lower position) only the white markings should be used throughout, but for later engines (post 1999, with the pulley higher the yellow markings on the belt should be lined up with the marks on crankshaft and those on the LH two camshafts (as you look at the engine from the front), while the white markings should line up with the marks on the RH two camshafts. I have to say it's difficult to understand this when the only difference is the position of the other pulley, which, if you're fitting the cambelt in an clockwise direction has not been contacted before you line up all the markings, but that was Gate's advice.
It probably doesn't matter as long as the crankshaft and cambelt markings are all lined up, and there is no slack in the belt between the two camshaft banks and the crankshaft.
The other uncertainty I face is that my early (1993) V6 engine has a tensioner pulley without an outer flange. This design was subsequently modified by Vauxhall/Opel to include an outer flange as well as the inner one, apparently because the flangeless pulley sometimes allowed the cambelt to ride out slightly and scuff against the plastic cover. You now cannot obtain the flangeless pulley, so I am assuming that it’ll be OK to replace mine with the fully flanged pulley in the kit. Gates were no help with this issue – saying that they had no records of the flangeless pulley.
The first thing I do with any new belt is check it against the old one by turning it inside out and stretching it against the new one with a screwsdriver at each end to stretch it out, to make sure it's the same length, with some stretch from the old belt taken into account.
I've done this with this kit and seems comparable, but now that the tensioner appears not to be pushing against the new belt leads me to think the new belt is longer, and the shorter backplate is required. The shorter gap between the tensioner and pulley would take up the slack that my current tensioner can't take out.
However I've checked the belt and it seems same length, this is what I'm wondering about, it's like a paradox of the gates kit!
My original plate says 6B on it, according to the video the later plates should say I think it was 01 or something, whatever it was it wasn't 6B.
The original plate from the first belt change was 6B as well so the one I just took off is the correct one to use.
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