Fuel filter to fuel pipes connections

[drmdrm]

Hello,

last week a fuel line next to the fuel filter at the rear drivers side got damaged. It is a small rubber pipe connecting the fuel filter with the fuel pipes that lead to the engine and also seperating the pipe into a second line that leads back to the fuel tank. The small plastic piece where the lines get seperated is the part that is broken. (see image attached)

Yesterday a mechanic provisionally bypassed the line, going from the filter back to the tank, and connected the filter straight with the pipes that lead to the engine.
The pipe returning to the tank is now unconnected.

I asked a few other mechanics and they all didn't seem to know what the purpose of this return line is, what the effects on the engine are if it is unconnected and where to get a replacement for this connector/pipe.

So I wonder:
What is the return line for?
What are the effects on the car if I drive like this?
Where can I get a replacement and how is that part called?

Thanks for help!

[wahiddd]

The hose is return line to fuel tank and 4bar fuel pressure regulator in the fuel pump assy
Its to bleed excess pressure over 4bar and maintain 4bar fuel pressure in the fuel pipe until FPR on fuel rail