Spark plug wires was one of my guesses too, but that didn't fix it when I replaced them. The stumble occurs In a very narrow part of the acceleration curve. The O2 sensor voltages actually drop to zero and sometimes show a few thousanths of a negative reading at this point, probably indicating very lean combustion. Just for kicks I unplugged the AMM, which had no effect on the stumble. The stumble is consistant, occuring on all low rpm acceleration from a cold start to a full operating temp engine on a hot day. When I press down harder on the accelerator, it will break out of the bad spot and accelerate smoothly right on up to cruising speeds, (if I keep the rpms up). If I accelerate slowly, the car stumbles and hesitates at that same rpm spot through each of the gears.