I'm trying to figure out whats going on with my truck. My tune calls for 104 octane race fuel. Well the track here only sells 112 octane. So i been mixing about a quarter tank of 93 in my truck with 5 gallons of 112. Well my exhaust tips are snow white but my plugs are dark brown. I thought they should have been white like the exhaust tips. Am i mixing to much 112 and my tune isn't set up to burn more octane? Would this cause the dark brown plug tips? I had it retuned in january after installing my longtubes and Circle D converter. After the tune i have not been able to come close to my best 12.26 run. I know the weather has alot to do with it, but my 60' went from consistent 1.68's to the best of 1.73. My best pass was before my retune after the header and longtube install, after that it has not come close. Any suggestions on the fuel?