Just received a call from Buckhead a few minutes ago, Thomas told me they put OEM plugs back in it and stayed with the stock heat range. According to him, even the E55's running HIGH amounts of tuning don't even go with colder plugs... I was under the impression there are several people running with colder plugs, but I guess they aren't dealing with the heat from the 61mm pulley like I am. All of that is a bit over my head, honestly.

They are also going to put it on the dyno and scale down the injectors a bit.

I asked about the color difference in the two plugs from the same cylinder, he said the lead plug usually fires just before TDC on the induction side, while the trailing plug fires milliseconds later during exhaust stroke.

Makes sense to me...