will not idle after warmed up

I have a 1989 wrangler 4.2 carb auto trans. It was running fine but needed whole exhaust. I had exhaust replaced form manifold back ( new cat new emmision tubes) now it runs good on fast idle and then stumbles / stalls when i stop. I thought vacume due to me putting hand over part of carb and idle coming up. I replaced O2 this weekend, changed out some cracked vac lines but still not happy. any help would be great.

Had a similar problem with my '98 TJ, my problem was a high idle and poor gas milage turned out to be an idle control sensor, it is located ontop of engine. Don't know if this helps, I had high idle, but could also go the other way maybe???????