I seem to have a vacuum leak, my car has new plugs and wires, but idles rough. I think it's a vacuum leak. Is there a way to test for this??

 

and what engine do you got? SL...?

 

1985 380 sl vin#wdbba45c0fa033825

 

Once at a smog inspection station the tech suspected a vacuum leak. He sprayed something from an aerosol can along the intake manifold. It was very evident when he passed the leak area as it killed the engine(6 cyl). Maybe a parts storecould tell you what he used. Or check with your mechanic if you have one that you know well enough.