Fuel pump problem
 

I have an Audi a4 (8E) 1.8T, 120KW, Year 2003.
After changing the fuel filter it starting making noise near the fuel filter (or near the fuel pump, cause I'm not sure).
At the service told me that I have to change the fuel pump.
I have installed 3 fuel pumps till now. They seem to work good, but in the morning the engine starts with dificulty.
I don't know if the fault is because of the fuel pump that maybe is not genuine or from other reason???