I have replaced the coil and cyl head temp sensor and it's still running rich. My exhaust temp has never exceeded 1250 so somewhat leaner will not hurt the pistons. I've been told 1400 would be ok. Nissan suggested the NGK GR5 plug [hotter]. It is now 3/4 black and 1/4 dark brown. I am willing to adjust the AFM but have no idea of what to do and how much!