In Winter I waited 2 hours and a half at the entrance. Tried also to ask at the gas station but really few cars. Most of the traffic was going nearby or in Napoli. I had a sign Salerno and managed to get only to the next gas station

It's no good to go south, most of cars drive to east, but you can try. You can stay on the other side to go in direction Salerno, there is a free way between stations.

Agip petrol station is the biggest and best. Lots of people going to Salerno. I waited very few and reached Eboli very fast, after continuing the Cilento region was poretty easy