Hello Si. Do you still use the early RXXX K-series ignition setup with a distributor on the end of the inlet cam? When I ran my old 200bhp engine using a distributor and VVC head, I cut-and-shut some new Lucas £20 VVC ignition leads by chopping them down to a suitable length and grafting the distributor ends on, retaining the longer VVC plug ends. They worked perfectly for years, lost zero power and no need for snazzy leads! However, if your current leads work fine, I'd be tempted to leave them alone. I think DVA has suggested that non-VVC Magnecor leads (and possibly some other brands) can have their spark plug connectors pulled through the boot more to work with VVC heads. Maybe your leads have had this treatment?