1992 ck 1500 5.7 rough idle when warm

I have racking my brain on this one the truck runs great when you first start it when cold but when it warms up it runs really rough and when yougive it gas it jsut doesn't wanna go there is no smoke or any thing coming out of the exhaust so i don't think its runnin rich but heck i really have no clue any takers on the mistery please help anyone

i think i have the opposite problem. it runs shitty for the first minute or so after starting. i have to rev it up a few times before it really kicks into proper idle. runs like a top when it's warm but not at all when it's cold.
sometimes i get a little black smoke and tiny water droplets on startup too.
can't figure that one out.
edit: that's probably not helpful.
a 92 is a TBI engine, right?
is the MAF old? air temperature sensor?
the engine should be adjusting fuel flow according to temperature and airflow. check the common easy things first.

Might be a good idea to have the exhaust back pressure tested when the problem is happening. Could be clogged cat or exhaust.

//2000CAYukon