As per the title - my recently purchased '09 Mondy 2.0 diesel (low mileage) will sound noisier and more 'tractor' like after starting sometimes. This is most noticeable in 2nd gear above 2000 rpm. The weird thing is, this will occur for an entire 'journey cycle', but switching off and restarting will stop it. No power or performance issues. 

Any ideas or should I stop worrying?

Edited to say - I've noticed that on the occasions this happens, the CEL stays illuminated for a couple of seconds longer than usual before turning off.

So it's 3 weeks later and the oil warning light came on on the dual carriageway, starts knocking shortly thereafter prior to shutdown. Pop the bonnet and there's oil EVERYWHERE all over the right hand side. Definitely not a slow leak/mist as had the bonnet up yesterday filling the washer fluid! Had it AA'd to my local garage and waiting for them to open.

I'll keep you updated as this clearly started out as a minor niggle, but first impressions of this car are not good. Bought this car as only has 20,000 miles, I'll bet the knocking's just added 60k's worth to the engine!

hope it is not to costly for you