did you figure it out yet ? i got a 2001 gt doing the same thing, runs like a sewing machine, tranny changes fine, but every now and again, very randomly, that sucker will just, jerk or stumble not really jerk but just a miss, once or twice very quickly, then back to normal, no check engine light , have noticed it doesn't do it at high speeds on interstate. rebuilt trans. last year, new plugs, wires, 1 coil, new map, cleaned maf, new pcv, new speed sensor, does this sound similiar to yours ? mine was bucking bad a few years ago and it turned out to be the map sensor, gasket had gone bad on it, this is similiar to that but isn't it and no code HELP anyone ,,,