need help with idle problems

[method2833]

for some reason, my '91 keeps dying. it seems to do it when I decelerate hard, or sometimes just under normal deceleration. And sometimes, fairly frequently, under deceleration, when i'm almost stopped, the car will go to like 200-300 rpm, and almost die, but when i get completely stopped, it goes back up to normal idle, and runs just fine. I seem to get these problems more often when it's raining or damp outside. Could it be a sensor somewhere, like the MAF? Any help would be appreciated. Thanks