Dude, you should be able to tell at a glance if the choke is sticking or not.  Just look down the throat of the carb when the truck has warmed up to see if the plate is opened up or not.  There should be 3 or so screws holding the choke body in place, if it's not opening loosen those slightly(after it's fully warmed up) and slowly rotate the choke housing either way and see if it moves.  I can't remember which way cause I haven't had a stock carb for so long, but it'll move no matter which way you rotate it.  I personally like the water choke on my weber.  If it's not that and not either idle adjustment then I would suspect a vaccuum leak.