1999 Volkswagen Beetle mechanic can't figure it out

Have my beetle in shop. They said it was fixed, before I got home it began to run rough when I stopped. I took it back, it has been there a week and they can't figure it out. When you turn on anything electricall it makes the engine run rough. They believe it is a short somewhere but can't find it. Can you help? It did not do this before I took it there the first time. They replaced oxigen sensor, mass air fow sensor, plugs and wires and tail light switch and headlight.