I bought a 91 Zephyr a year ago. It is such a cool old girl. I have been working hard to make it better all the time without altering any standard features. It has been purring like a kitten till afyet my last ride. I filled the tank after a four hour ride and parked her up. A week later I washed her and started her up. She was missing straight away. Accelerating away it stutters then clears and powers away. The missing wont go away. Have changed plugs. Checked the leads. Drained the fuel tank and put fresh petrol in with a new fuel filter. She still is missing down low and clears under acceleration. Any ideas? Can the coils cause this or a carby issue?