Your situation sounds kind of similar to what my '92 K1500 was doing when I bought it. I had to put a new catalytic converter on it before it would pass smog. The shop said that it was fairly common for the electronics in the distributor to go bad, causing a rich condition that would ruin the cat. For the most part the truck ran good. It would stall at idle when warm. There was a miss too. It soundsed like the shop was trying to ring more money out of me, but I wanted to get rid of the stalling at warm idle. I installed a rebuilt distributor myself and it never stalled again. The slight miss continued.
I was putting new heads on the truck recently and met a mechanic friend for lunch. We were discussing the truck and it's history and he asked if I changed the O2 sensor. I had not. He said if the cat was bad the O2 sensor was probably compromised too. I replaced the O2 sensor while I had the heads off and the truck runs like a new truck now.