skoda octavia combi engine cutting out/shudder while driving approx 1500rpm

Hello,

I have a 2012 Octavia combi 2.0tdi 140bhp with intermittent engine cutting out while driving at approx. 1300-1500rpm and has also stalled while trying to move off from junctions. just no power. the car starts every time hot or cold no problem after it has cut out. And the fault is intermittent theres days it will be fine or be a right B***H!! there is and are NO FAULT CODES at all when it does this. I have changed the fuel filter with a genuine skoda filter. I had noticed the filter housing was damp and the cap was slightly warped/ raised. I thought it could of possibly been drawing in air into the filter housing. straightened cap replaced o-ring and greased to help seat correctly. day went by no problem and bam she started to muck about again. this has started to develop over the last couple months. I use good diesel from a reputable garage.   im stuck for ideas where to go pretty confident its not electrical and dash does not cut out pretty sure its fuel related. thinking start at the tank and work forwards. or if anyone has had problems with this engine