For those of you following my search for an ECM, I finally managed to secure a unit out of a 1986 Corvette. ECM is number 1227165, with PROM "BUA". I installed the unit, and the engine sounds much healthier while stationary, and does not seem excessively rich as it did before, though it seems to have a great deal of trouble when under load. It bogs down severely and hacks and pops during acceleration. The "Service Engine Soon" light, which worked perfectly with the last ECM, flickers briefly whenever the ignition is first turned on, and will flicker or illuminate occasionally while the engine is running. Field service mode does not work, and the light only turns on for a second or flickers a couple of times when I enter diagnostic mode. There is no code 12 or anything. Does this sound like a bad ECM? Please help me figure out what the heck this is. I would be especially interested in hearing from those of you who have had to replace ECMs. Thanks.