1978 Other Porsche Models Fuel system

Hello, My 924 had a recent fuel filter change. Before I had to pump the Gas Pedal to get the car started. After the Fuel filter change, I could never get the car started. I took it to a mechanic, and put it to a machine and siad all electrical components work (Fuel injectors, Fuel pump) All cylendesr are getting fuel pressure except the #2 cylender and suggested we replace the #2 fuel injector line. We did it and nothing. He said he found fuel leakage with the Fuel accumultor but didn't know if it was the Fuel distributor(Is this the same part) Could it be any other part? Such as the Cold Start valve (what does this part do) Fuel Level Sending unit(What does this part do), Fuel pump check valve(What does this part do), Fuel Sender (What does this part do ) Oxygen sensor (What does this part do?) Thermo time switch (what does this part do?) I would appreciate an answer and will donate for a quick response