Reading spark plugs

[speED]

Hello everyone, this is my first post to this forum. Curious to see how some of you read spark plugs in reference to air/fuel ratio. As a previous drag racer I was taught to make a WOT pass and look at the base ring on the plug. Now that my race engine is in a street car I'm concerned about idle and mid range as well. I recently read an old popular hot rodding article that said to read the porcelain. The top area is idle, middle is mid range and if you cut threads off plug the lower section is WOT. any input is greatly appreciated.