As we have all seen, there are many articles out there for spark plug tuning at WOT but not many about street driving. The article that I like to use describes reading the spark plug as:

* The "Ground Strap" = Heat Range
* The "Plug's Base Ring" = Jetting
* The "Porcelain" = signs of preignition/detonation

For WOT, the bottom of the plug (base ring) should be covered with color for 7/8 to 1 full turn. For street driving, once again, there are not many articles or any that show what this should be.

Your plugs appear to be a perfect color for the WOT plug (see below picture) but it is a street driven car. I am going to say that since you have a full turn of color on your base ring, no signs of black specs on the porcelain (except it does seem to show a tan color down on the around the side of the porcelain), I am going to say that your "street driven plugs" are a tad on the rich side.

I had my plugs looking the same as yours on my streeter and I decided that since they were so close to the typical WOT description, I dropped my main jets down by 2 sizes. This changed the color on the base ring to apx 3/4 color all around (instead of the 1 full turn of color) and I have no signs of detonation on the procelain and no ping at WOT. I also think that the color on the porcelain will change due to the strength/condition of the ignition system on a street car.

Good question and I hope you get more responses explaining the opinions on the lean/rich street plug. I would have no problem with increasing my primary jetting back up two sizes if someone can explain why a steet driven plug should look like a WOT plug description.

BUMP!!

Note: The below shows a WOT plug.