Engine cuts off when driving?

I have a problem with my Iveco Daily 2003 with engine 8140.43N 2,8 tdi commonrail.

The problem occurs when I´ve been driving for some time (could be 50km or 200km) then the engine just cuts of and the red warning light that looks like an injector flashes. If I press the clutch pedal and wait for 4-5 seconds the warning light stops to flash and then I just release the pedal and keep on driving.

It can take some time before the problem starts but when it does it´s coming back in irregular intervals.

I feel that the problem is increasing and I can´t relax when driving.

I´ve changed the low pressure pump and the pressure regulator with no luck. Iveco has checked the error codes and they say that its a fuel problem, and I agree about that. But what can cause the fuel to cut of fo 4-5 seconds (always the same time)? Iveco doesn´t know.

This problem never occurs in city traffic, downhill or plain ground, only uphill. And it don´t have to be much uphill, and not every time its uphill.

I feel lost

(sorry for my bad english)