1993 cutlass ciera 3.3L accelaration problem

I have a 1993 ciear that starts fine and idles fine, but when I give it throttle it acts like it is bogging down. It will not take accelaration. I have changed the plugs, wires, checked the coils and have replaces the boot in the fuel tank, changed the fuel filter and sent the fuel injectors out to be cleaned and balanced. What could be the problem?