I do agree with Ian - Planenut - Take a better view to the filter.
The filter regulates - at the end of the fuel line system - the requested 58 PSI back pressure for the fuel.
When the filter is really clocked you will see High pressure.
So it really looks like you have a very dirty filter.
Far better is to change the system.
Install after the injectors a real fuel-pressure regulator from f.i. Fuellab # 51501 and keep it on 4 Bar - 58 PSI. You can install a gauge on it. Th 58 PSI is not strict but 70 Is far too much.
And change the fuel-filer by an ordinary filter with filters directly the fuel coming from the pump before it goes to the injectors.
You can use the same original type of MANN fuel filter for it too but in that case change the fuel direction and block the back-pressure inlet of that Mann filter.
This is also a better solution for your injectors, because in the current situation the fuel is filtered roughly in the pump by a simple strainer.
The fuel is mainly filtered after it is used - Yes a very stupid design - so it can contaminate the injectors ( a strainer is not enough for a sensible injector ) .
Changing the fuel direction at the filter solves this problem.
Most of us have had the same problem and solved it like this I presume.
