Hello all - thanks in advance for any advice you could give me!

I have a 2010 Focus 1.6 tdci, with 82k  and it seems to lose power intermittently for no reason. I have had it about 6 weeks but after downgrading from a 2lt tdci Mondeo a bit I thought it was just me not used to it but I am now sure that I have a problem.

The best way to describe the issue is when the car is started its fine (perfectly normal response that I would expect). ( although on a few occasions it has seemed a bit lumpy.)
However after a while, or once the engine gets up to temp, at very random times sometimes over a week the power of the engine disappears, as if the turbo was missing (i.e. the engine has no sense of urgency, and there is no boost/shove from the turbo).

Now while this happens, fuel economy stays the same, no warning lights come up on the dash and under hard acceleration, it is not producing any excess emissions (i.e. no cloud of black smoke).

What makes this extra strange is that if I stop the car, even for a few minutes turn the engine off and back on again, she instantly has all her power back with the turbo providing the normal surge you would expect at 1500- 2000 rpm. Another issue which may be related is on 2 occasions I have pulled away and at about 30mph and the power will pulse up and down rhythmically as if the turbo doesn't know what to do .. it's going into the garage weekend to see if any fault codes come to light. Fortunately, it is under a RAC warranty I got with the car, thankfully.

Just a quick update....the garage  has put a diagnostic on the car..it has thrown.up 4 instances of a sticking EGR valve and will replace it...It  has been suggested I should blank it off...is that worth it..??