yes, it was definitely either the ignition switch or the key cylinder, for the reasons i described in my orig post. it ran for a couple of months with no problems but then choked again. not sure which of those sub-components though. it works fine if i bypass the ignition switch assembly (i.e., "hotwire" the car). it seems i have to remove the whole assembly even if i just want to replace the switch (not the key cylinder/tumbler). and it is mounted on the steering column with shear bolts. so if i have to destroy the bolts to get the assembly out, then i figure i may as well replace the key cylinder too.