No!

I am well past the point of this being economic (either for me or the owner) but I do want to know what is wrong.

Fortunately the owner is not in a hurry and is being really quite nice about it.

The fuel pressure issue was a bust (I thought that the pressure was too high, but a new regulator made no difference so either it is meant to be like that or both of my fuel pressure gauges are faulty in exactly the same way!)

I have managed to take a pre cat sample by removing the egr valve, it is not perfect (There was clearly some leakage resulting in higher O2 levels than might be present) but it is clear that the pre cat HC is way too high (500+)

I also did a compression test, 3 cylinders were 220PSI, one was 210PSI. I would not normally have regarded this as a big issue, but coupled with the high HC and earlier comments about valve damage as a result of not using the correct fuel, a nasty picture is beginning to form in my mind!

I would be grateful for any links referring to the valve issue, despite searching I have not been able to find anything on line.