Maybe excess carbon on the pistons making hot spots.
Got my MPS 3.6" pulley from ZZP today. Threw it on and went for a run. Surprise, surprise, I'm seein about 1* of KR. WTF! Mods are in my sig. I guess I'm gonna try some ssac headers next. If that doesn't cure it, I'm gonna start a L32 build and go from there!
How do I cure that?
Have you ever sea foamed your car?