My engine had been running a tad lean. I rejetted it to my liking and I’m shooting for a very light tan plug reading. The plugs were previously fairly white and it’s now tuned to my liking. I didn’t pull other plugs, but #1 cylinder I did. There’s absolutely nothing wrong with my engine and it’s running a lot better now. But, this plug reading is weird. I tried to take the best pic of it I could. If you look closely the plug burn is split perfectly down the middle like someone cut it with a laser. Left side is where it use to read prior to jet increase and right side is the reading I was shooting for. I’ve seen this once or twice over my life. But, have no idea why a burn splits perfectly down the middle like this ? No big deal, just curious as to why ? Autolite 65, soon I’m going to switch to a slightly colder plug, Autolite 64.