Spark Plug Diagnosis Help

[CptnVortex]

So, these plugs have about 10k km since new. My thoughts are that they were running lean? The other 4 plugs are like the one on the left, more white than black. I could have sworn I was running rich as the car was popping and grumbling like mad, and never overheated, before my Miller PSIK install. Now it just runs great, but I figured I would swap to new plugs anyway. Thoughts?

[jlevie]

If most of the plugs are like the left one in the first image, those cylinders are normal to slightly lean.

[CptnVortex]

Hmm that it what I thought, from the chips on the ceramic was my guess. Will do a few hundred K on the new plugs and check them again to see where they are at now.