First was noticeable at idle, sounded like a timing chain rattle in the wrong place. It was the side of the air filter box that had broken away prompting me to write this thread. If yours is like that, consider removing the baffle, which I'll do next time I pull mine apart.
Second was my turbocharger - the bolts holding it to the exhaust manifold had loosened and the exhaust was leaking. The gasket was making it produce a louder rattle under moderate load and under a light load, a strange whiny sound (much like a reed in a woodwind instrument) which wasn't exactly in time with the turbocharger so it had us guessing for a little while.
My first thoughts with this issue was if a snorkel was fitted it could be two things. The growl/whistle noise is very noticeable, some snorkels even factory can rub and vibrate under load on the bodywork, The d40 my mate has the baffles in the box became loose and it did the same.
HJ