Quite comprehensive. Good I had this experience. I have a motorcycle with a small 125 cc engine. It's a twin spark motor. Both spark plugs are of the same heat range/ rating. I once thought of switching their positions with each other. So I did and started the bike. Lots of misfiring, poor pick up, overheating, loss of power. So after cool down I switched them back to their original position. And everois perfect now as before. Never did it again and will never do. What could be the reason.?