Just red your mail warmshed and got myself thinking it's a shame they don't do Sparktune for twins with two of the dodahs, then a light came on, long time ago I bought a set of those neon spark indicators from Halfords, you plug them onto the plug and the HT cable plugs into them in turn and they glow when the plugs sparking, I bought a set , they come in fours, I know I've got one in the plug box where the other three are could take a month to find out, but with two you could see if both plugs are sparking or just one