Surging w/No Check engine light

2001 4.3L 4X4 - I am in the middle of trying to find out what I should be looking at to troubleshoot a surging problem. I recently had the Random Multiple Misfire code as well as the O2 sensors come up on the code reader at my local Autozone. They suggested a tune up and O2 sensor replacement as I had bought the truck used and had no idea as to when this had been done last. With 80,000 + miles it appeared to never have been done, so it needed it anyway. The O2 sensors have a shield over them with slots in them; these were completly plugged with carbon which was not allowing any gas mixture to reach the actual sensing head. I gave it a complete tune up including cap, rotor, wires, plugs and air filter. I also changed out both the before and after cat O2 sensors. The Check engine light went out after driving it to work about three times. Now I am experiencing a surging condition accompanied by lack of power (sluggish) and some erratic shifting as a result, but no Check Engine light. My research at this point indicates the following possible culprits: EGR valve, Fuel pump and/or fuel pump pressure, plugged catalitic converter (remember the O2 sensors were completly plugged...why not the cat too?) Any other suggestions as to what I should be looking at?

I just had a surging problem, and it turned out just being a vacuum leak.
Mine is carburated though, so this might not apply to you