Never heard of that one before but looks allright.

I wonder if the higher the pump rating as in 255, 30 , 340, 400...it means that if I put a higher rated faster flowing pump that my fuel consumption will go high too, as in if I used to get 400-500 km per tank I'll get like 200-300...
Or will it just pump the amount required by the engine depending on how I'm driving? I'm a bit lost by how that goes.

All determined by the ECU & How it is tuned. If you only have an OEM/Stock Tune & have one installed. It will operate at stock parameters & you will notice no benefit/loss.

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Having a modern day PC without an SSD is like hiring a hooker for hugs.......

OK so if you get your ecu tuned and install a 320lph, does that automatically mean that your fuel consumption will be more than if you installed a 255lph pump?
Will it always pump at 320lph on acceleration or will it pump progressively, as in If I'm not flogging it, it will consume normally and pump at whatever lesser rate?

You might to google how a fuel system in a modern injected 4 stroke motor works.

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^^^ whs

its a flow & return system, pressure behind the injectors is maintained by the fuel pressure regulator, excess fuel send back to the tank yardi yarda...