Tandem Pump Supply Pressure

Hi,
I have been trying to resolve a long standing issue with rough running on my 1.9tdi,atd PD engine golf.
The car lacks initial acceleration when pushed, in addition on a light throttle around 2200rpm it feels like a missfire/stutter.
The car has no fault codes, has had a new turbo, new N75 valve, new injector loom, the vacuum system is good, the egr is all good.
The injectors are within +/- 0.5 at idle, torsion value is 1 and hasn,t changed.
If i connect a pressure gauge in the fuel line from the fuel filter to the tandem pump, at idle i get 7.5 to 8psi,(engine running) if I then rev the engine to 1800pm, the gauge fluctuates between 5-8psi really quickly, is this normal or does this indicate a problem with the tandem pump (the intank pump has been replaced...with no improvement)
Can anybody confirm to me that this is a normal condition or something not quite right !.
Thanks

Does the gauge movement stop if you rev it higher or is it just at 1800? I don't have any answers, but this is an interesting problem. Did the thread linked in my signature give any insight?

Hi,
The large increase in gauge movement only occurs above idle,typically above 1800rpm, then carries on to the max revs that i used during the test (approx 2300rpm), and were repeatable throughout a number of tests, the size of movement does not increase once it starts.

I have been using the PD lift pump guide by DanG144 as reference, but the guide doesn,t state if the values are expected to be steady.