1992 Chevy Lumina car help

My 1992 chevy lumina Z34 (3.4 lt dohc v6) starts to shakes when I first start to go then again around and 60. One morning I started fine went were I had to go and about 7-8 hours later it woudnt start. I was told it was the fuel pump and I jus went out and bought a new fuel pump, strainer, and filter and put them in and when I first tried to start it, it wouldnt turn over then about 2 tries later it did and stayed on but then I tried to start going and it stalled I was able to start it but only way to keep it on was to keep my foot on the gas and thats how I had to drive it. Is this a fuel delivery problem? Ignition problem? Or could it be the spark plugs?