Camshafts and Compression
Bruce discussed this with Mattax about his engine a long time ago. If you don't evacuate the cylinder what is left over becomes part of the next cycles AFR.
What are you using for headers and exhaust Valman?
Its the same. Plugs tan in America like they do in Australia. Grey is usually the plug working in exhaust gas residual, ie the chamber doesn't exhaust very well and the left over exhaust hangs around and is present at the next ignition event so leaves a grey colour.
Bruce discussed this with Mattax about his engine a long time ago. If you don't evacuate the cylinder what is left over becomes part of the next cycles AFR.
What are you using for headers and exhaust Valman?