i had same problem with my 2.5crd and 2.8crd  the 2.5 i replaced all filters (not housings)had tank removed and cleaned no luck sold car in the end  my 2.8 had exact same issues  changed all filters fuel filter housing(ie heater/manual fuel pump) still same issue  sent to diesel specialist diagnosed fuel rail pressure release valve  cost few hundred quid to diagnose and get sorted but 2 years in now and im still going strong  my advice is send it to a specialist who knows what they are looking for  my experiences with 2 voyagers the fuel systems seems to be very temperamental there are post on this forum about these problems already as well as a big write up on the web somewhere that i read ps when you get it sorted only use premium diesel cheep diesel seems to worsen your problems