Yesterday as I was driving to work my truck started running rough, it started running sluggish, revs on its own, lunges, stalls at stop light unless you throw the automatic in neutral. I read an old posting here that someone had the same issues as I am having now, I changed the IAC on my truck as everyone recommended on the old posting. Long story short I am still having problems and I don’t know what is the issue.

The truck is a 1991 Silverado Dually Extended cab 3500 with a 454 engine 7.4 liter.

any thoughts?

Thank you.