Car has a loss of engine power, fuel mileage and is running hot

I took it to a shop paid for a diagnostic and was told it was the fuel pump, very little fuel pressure. We replaced it Friday and it still has the problem. Still no fuel pressure with new pump and and new filter. All fluids are fine, we have done the air filter, fuel filter, wires, spark plugs, etc and I am frustrated and worried about becoming stranded, a little hard to start now in the morning too. Any ideas?? Now I am being told that the fuel pump they put in is bad, hope it doesn't turn out to be catalytic converter