No problem mate, I would say in that case that it would be more of a pump problem than anything, I've worked on transits for the last 12 years which have the same engine, the fuel rail pressure has to be within a certain tolerance, I think it's 50 bar either way, or it will go into limp mode and put the light on, but then be ok when you restart it. Ideally you could do with monitoring the fuel rail pressure under load to see what's happening.

Hope that helps?

Karl