Ok that all makes sense, FWIW my Cossie has just had a rebuild, done by a mate so I can't prove it either LoL.

Oh, just a thought, does it use oil? That's the most noticeable difference between my Cossie before the rebuild and after - sure it uses oil after the rebuild, and the turbo is in good nick too - but before it needed topping up every 200-300 miles (max-min on dipstick in 200-300 miles I mean, less if hammered).