For the past week our '88 has been doing the running rich thing. Just as others have described; warms up normally, then gets richer and richer 'til she won't run at all (just like my '76 Fiat that used to die from carburetor icing). Shut if off to clear the ECU and it's fine for about 2 minutes. After a week of poking and prodding I discovered two things that could happen to anyone. The wiring inside the rubber boot on the AFM plug had broken for the second time. I finally figured out why. Occasionally when I open the engine hatch, it will slip out of it's hinge slot and drop the metal tongue directly onto this connector. I think that this actually broke when I was removing it to test it, so it was not the reason for the running rich. The second thing was the wiring to the plug for the O2 sensor. Underneath the rubber boot on this green wire, the insulation on the inner signal wire (this wire is coaxial with a grounded wire around the signal wire) had cracked and broken just enough to allow the signal wire to be grounded against the outer coaxial wire. I only noticed this because the wire seemed too flexible at this point. I wrestled the rubber boot back from the plug and there it was. I spent many hours of evening trouble shooting and missed this stupid little failure. Thought you all might want to know.