New plug resistance testing:

Plug___RES___Cut off___Var (out of range)
1_____4.5_____5.0_____-0.5
2_____4.5_____5.0_____-0.5
3_____4.7_____5.0_____-0.3
4_____5.2_____5.0_____+0.2
5_____5.3_____5.0_____+0.3
6_____5.1_____5.0_____+0.1

Gapped all plugs to 1.5. Oddly enough, the service diagnostic manual says 1.0mm. However in the service manual itself, it say 1.0mm - 1.1mm. So I chose right in the middle.

Of note on the 5.0 ohms cut off, that's something I read in two articles as a benchmark ohm resistance reading that you should use to make the keep or buy new plus decision. It doesn't state that in the factory service manual.