1994 Oldsmobile Ciera

Engine occasionally goes into a mode where it barely idles, stumbles and dies. If I run it for 5-10 minutes, then let it sit for 10-20 minutes, it will run fine. This typically happens when I attempt a cold start on a warm day, particularly in wet weather (I live in southern california, near the coast, so warm day means 70 degrees). It has never happened on a workday morning, when I start the car at 6AM (before the dew condenses - I park the car outside). In this mode, the computer has kicked out cam sensor, cranshaft position sensor, accelerator position sensor and EGR faults at one point or another. I have replaced all of these, as well as the O2 sensor, the coolant temp sensor, the MAF sensor and the MAT sensor. I have also replaced the plugs, plug wires, ignition module and coil packs, and I have had the Pep Boys injector cleaning treatment done. Unfortunately, whenever I have taken it in, they have been unable to duplicate the problem long enough to troubleshoot. I kind of think it has something to do with moisture, but I'm not sure. Interesting point - the problem occurred yesterday (semi-drizzling, after a very wet friday), but today (sunny) it's fine. I went out an poked around a little in the engine. When I disconnected the O2 sensor, the "check engine" light did not come on - I would have thought it should have. Please give me any ideas - I'm pretty much at wit's end.