Fuel tank/line air leak problem - 313CDI

Hi all,
I think (thanks to Vic) that I've narrowed my cutting out issue down to air getting sucked into the fuel system somewhere on the fuel tank side of the filter.

So - could I ask for ideas please on the most efficient and cheapest way to approach this? Where's the most likely place for it to be taking in the air?

I've never seen inside one of these but from the EPC it looks as though there are loads of parts and I don't really know where to start. What should I replace? Are there any particular seals that are known for giving trouble? Should I replace the fuel lines to the filter?

And what about the breathers I've been reading about in poolmike's thread - https://sprinter-source.com/forums/showthread.php?t=9421 ? Are they likely to be the cause of the trouble? I do tend to get a vacuum in the fuel tank - I can hear the air rushing in when I take the filler cap off.

Any help gratefully received. Many thanks as always.

Bruce

Rockbeer.
A comon mistake is to replace the factory hose clips with worm drive clips, this will cause an air leak because worm drive clips do not work on small diameter hoses because the worm part stays straight and will not press the hose down on the pipe. Binding the hose with steel wire will be better than a worm drive clip. Eric.