You mentioned color on the threads, I looked this up and found nothing about it. How can thread color affect performance? I've changed many a plug and sometimes the threads were the same color as when I installed them sometimes a little darker.Agree with above, but I’ll add your timing is one,two degrees safe. Cut a plug and have a look at the fuel ring. And if it were mine, I’d look for one step colder plug, you don’t have any color on the threads yet.
