My 406 HDi 110 is pretty quiet and refined for a diesel, *but* when driving uphill or in fifth at around 60 (and therefore giving it a fair bit of throttle) between 1800 and 2000 revs it's not. The car sounds noticably noisier than at any other point in the rev range, more diesely, whereas normally you can hardly hear engine noise. Accelerate though to 2000 revs or above and the noise disappears. Same for if you slow down, so it's definately not the engine labouring.
Is something broke or do they all do it?