Sounds as though you have tried pretty well everything. I have heard of injectors leaking back badly when hot, this could lower the rail pressure to the point that it cuts out. Run the injector leak offs into 4 similar sized recepticles and watch the ammount of fuel flowing which should be similar for each one, if the ammount varies by very much by the time it cuts out, the one with the most fuel will be faulty.

Failing that I would think its something temperature related.

In a way your lucky!

I had one in with identical symptoms except it ran for 18 min's,I had to make up a leak back tester usimg 250 ml juice bottles,

Fuel pressure ran at over 250 bar at idle but when the time got closer it began to drop,cut at around 190 if I recall,30 min's to cool down and it'd start up again.new injector cured it all.