Are these statements regarding spark plug reading correct?

1. To check to see if my main jet mixture is correct- drive around at high rpm for awhile then quickly shut off the engine. Then look at the porcelain furthest from the electrode. If white- too lean, if black too rich.

2. To check idle circuit mixture, idle the engine for about ten minutes, shut down the engine. Look at the porcelain closest to the electrode. If white-lean, if black- rich...

FYI- I do have an air fuel gauge hooked up. I just want to verify my readings.

My understanding is that the advent of unleaded fuel made spark plug reading archaic...

You can trust your A:F gauge... Have some faith

Unless you shut off the engine and coast the car to the side for the road, reading plugs these days only tells you what its doing at idle, not when the engine is under load and you really care about it.

Zach

I don't believe its possible to accurately read spark plugs with modern gas

it works. its still a viable way to get you in the ball park but...
"in the ball park" does not really win the game
a wide band O2 is a home run

chalky white will run hot. sooty black could wash down cylinders and ruin oil