glow plug relay springs to mind as being a issue on these but i'm not 100% sure, try a google search.

just re-read your message, when it cuts out does is the fuel pump in the tank deffo working then? i'd suspect it would bring up a fuel pressure related code then but i know the intank pumps play up alot.

the snap-on machines are usually very good, it's just a case of working out whats going on.

i assume you've checked the glow plugs?

personally i'd be thinking towards a glow plug down and a intermittant fault with the intank pump.