07 transit connect diesel problem

[S0 What]

Hi there chaps, i have a connect in at the mo with an intermitant power loss, it drives fine but if you rag it in gear in the next gear it will hold back quite violently, then the power comes back in softly followed by a few sharp jerks as the power drops off again, it's more like the engine has shut off rather than a gradual loss of power, there are no fault codes.
I have driven it with a code reader instaled recording live data and all i can see if there is a sudden drop in fuel pressure, it will drop from 5560 PSi to 940 PSi, then as expected the revs drop fiollwed by the map and maf reading dropping until the fuel pressure jumps back up to 6000 odd PSi ?
I have changed the fuel filter and it made no differance, anyone got any other ideas?

There are no other problems, no smoke (of any colour) and it can go for days without the issue, IF you dont rag it through the gears, it has a new I/C, there are no leaks and it starts on the button without smoke, i regularly service the van and it's a no expense spared customer/owner, if it needs it it gets it, last job was to replace the EGR pipe as it had rusted through.
any ideas or experiance ?

[Getragdogleg]

My transit (full size) would do the same, after months of going back for scans and changing stuff I accidentally found that if I moved a big tube full of cables that ran from the inner wing to the engine block the engine would cut out/die , then if I moved the cable bunch back again it would be ok.

I undid the ribbed tube and found a few wires rubbed through that would touch and short when I accelerated, the condition was worse when the weather was bad as there was also water int he tube to help the short !

solder/heatshrink and new tape and it's mint again.