fuel test help

hi all
i got a d2 td5 and i did a fuel test on it to day
my readings was 4 bar then i started her up the the needle was up and down all over the places is this normal ?
i did the test from the temp sensor port

Fuel temp sensor port is upstream of fuel pressure regulator thus should read 6-7 bar. As engine takes fuel this should drop a bit but not below 5.5-6 bar at full boost.

Two options, either FPR is fubar (not holding pressure) or fuel pump not delivering enough volume as to keep pressure up (partially plugged or fubar).

thanks for that the fpr is new but am sure in my mind for months this as been the prob
the fuel pump is new as well but the lack off pulling power was the same with the old pump so my be the fpr is dudd from new thanks a gen

hello me again just put a new fpr on from land rover £140 and still no look the fuel pump is new to so what the prob now any one now