Expert 2.0 Hdi 2000 Model year

[Horsepig]

Evening all, I've just joined the forum.
I'm sure someone has had this before and there may well be threads on it already (if so, the links to them will do fine), my problem lies with an expert van, 2.0 Hdi 2000 year and concerns fuel rail pressure. What is happening is that the van starts and runs fine, then, after a period of time, no pattern to it, it will stall and the diagnostic light will come on. It will start again, eventually, and may run well or stall again shortly afterwards depending on how it feels. I've had the diagnostic machine on it to read the code and it was indicating fuel rail pressure. The mechanic decided it was fuel pressure regulator and changed it. It ran well for 2 days, on the third it stalled when being parked but the diagnostic light didnt come on. Today it stalled again and the light came on and it was difficult to start. I took it back to the garage and all the way there it stalled, but when we went out on a live test with the machine connected it didn't!! The fuel filter was then replaced and inside the fuel filter can was a half inch piece of silicon at the bottom.....!? No idea how on earth that got there. At the moment it's running ok again, sometimes slightly hestitant but it hasn't stalled again. What else is there to try? Has anyone else had this problem and cured it?
Thanks.