[Dancake]

The high pressure lines are supposed to be replaced each time they are removed. This is because they deform when tightened in order to provide as secure a connection as possible. You can reuse them a number of times though, providing you don't overtighten the nuts. Unless the pipe is damaged or leaking I wouldn't be rushing to replace it.

My recommendation to try the FPR was based on trying the easiest thing first. It obviously didn't work despite some of the symptoms matching those created when a fuel pressure regulator starts to play up. The fuel pump is a strong possibility, but before you go near it I would pull the fuel filter and check for swarf in the filter housing. If you see any take a picture and post it up.