vw afn pasat ,,head scratching fuel issue help

[pjbisforme]

going along and loss of power occurs suddenly ,,,its not in limp mode and is staying that way for a few days now ,,,tried vcds lite no faults ,,swopped maf no difference ,,disconnected maf no difference ,,, checked fuel return from pump which is good ,,,,its boosting well upto 20 psi ,,,,i have a vac guage on fuel ,line and its a good reading ,,,this is twin tanked with veg oil ,,,runs just the same on veg or diesel ,,disconected battery for an hour no difference ,,disconected engine temp sensor no difference,,,, swopped n75 valve no difference ,,swopped inline sensor on intake tube no difference ,,,turbo seems to be working well ,,need someone technical on this one ,,,i have a spare pump ,,but can i just swop it or do i need to code it to car its an r reg passat ,,,was thinking of swopping fuel compensator but sureely if that was duff it would bring up a fault code ,,,no cel at anytime ,,,tia