My wagon stutters on hills

93 wagon 3.3 automatic. After replacing the fuel pump and filter the car ran perfect for about a 2 weeks.. Now going up a hill or putiing it under a little pressure, the car will start to stutter.. If I give it enough pedal to kick it down a gear, the car will stop stuttering and take off like a rocket. I know it isnt the cat converter(because there isnt one on the car, previous owner welded a straight pipe in its place :shakehead ).. Could it be that there is no cat on the car ? Coilpacks ? Plugs and wires ? EGR ?
All of the above ? Any other ideas ?
Thanks in advance for any help

Sorry i noticed i was in the wrong forum, please delete as I will post this where it belongs, in the buick section.

Your torque converter is on its way out....