Megane II loss of power above 70mph

[nc29]

I own a 1.5 dci Megane II and have recently encountered a problem while driving on the motorway. When I’m driving at 70mph + I feel the car is working a lot harder and noisier than it was before. I have no warning lights on the dash, oil and coolant are fine. Has any body experienced this and can point me in the right direction? Another point that might correlate is that my car has struggled to start a few times as well since I experienced these problems, maybe every 1/15 times. Thanks in advance

[alanf]

May need a new fuel filter