Running rich (sorry long)

About a month ago, I drove my wife's 90' notch for the first time in a while. I noticed it was running rough and began to investigate. I pulled the plugs and the front two were black and sooty indicating a very rich condition. I checked the filter and the fuel pressure and both were okay. As it progressively has gotten worse I'm running out of ideas. I've replace the coolant and oxygen sensor, checked and replaced the vacuum lines, swapped out the MAP sensor, cleaned and checked the EGR valve, removed the cat, turns out it was plugged but not the problem, checked timing, both ignition and valve. I've just about run out of ideas. Is there a way to check the computer to see if its bad? Any ideas what's wrong?