1987 Chevy Corsica idle problems

Hey all,

I have a 1987 Chevrolet Corsica, car has 76,000 miles, it has the 2.8L motor. The car will not idle, when started the car's idle jumps from what seems 600rpm to around 1200rpm. Sounds like the car has a big lumpy camshaft in it. Once going the car runs perfect, smooth as can be, when coming to a complete stop it starts doing it, seems more severe as it gets to operating temps.

Sometimes it will even die. But it always starts instantly again. Also, when walking around it while it's running, and idling funky, I smell heavy gas fumes.

My first thought is a vacuum line? Any ideas?