Idle issues...mysterious

So my 1987 B2000 is exhibiting strange and frankly, annoying, behavior. For most of the fall it has been relatively cool, and my truck has been running well. After a few pumps of the accelerator it typically fires up and idles fine in 30-40 degree morning temps. However, recently, the truck will fire up, but no matter what will not idle. If I don't press the accelerator at all it dies. Even after the engine is warm, if I approach a stoplight, it will die. The days have been warmer recently (near 74 degrees fahrenheit) and thats around the time it started acting up. I've perused the boards here and some suggestions for similar problems have been maybe the accelerator pump on the carb; or even vacuum lines. I'm hesitant to approach vacuum issues as I'm not familiar with all of the smaller components such as sensors etc which hook up to vacuum lines. Any ideas are helpful!!! Thanks

Do you still have the stock carb?

To check for leaks my mechanic sprays brakecleaner onto where the connections are, if there's a leak the engine will change it's tune straight away.

You could also try changing your plugs to a different heat range, it might be that the plugs are happier in the colder temperatures.

Appreciate the replies. The carb is indeed still stock. I've considered maybe cleaning it once more before maybe buying a new one. I've attempted the brake cleaner tracing technique on a couple of occasions for other issues, and didn't really find anything.