Jaguar Vanden Plas Engine Runs Rough

The Car Runs Very Well But I Am Experiencing Vibration Between The Speeds Of 45 And 55 Miles Per Hour. Less Than Or Greater Than Those...

The Jag Runs Down The Road Very Smoothly. When I Come To A Stop/start, It Idles Roughly. I Have Plugs, Wires And Coil. What Else Can I...