1991 900 N/A with EZK ignition. I'm getting some misfiring when cold, improving when warm but not going away entirely. I took off the plug cover and started it up in the dark to look for arcing. Didn't see any but, on reving, the entire lead would flash! I take it this is not normal?... There's a new distributor cap fitted and the plugs were checked and looked fine a few weeks back. I tried a set of leads from another car but with much the same flashing lead effect...