I returned yesterday from a weekend of driving at Infineon and noticed that instead of the usual black exhaust tips, I had rust colored tips. My concern is that the the last time this happened my car started to misfire and I had to replace the spark plugs, as they were incredibly glazed over. My mechanic said it was likely due to the previous owner running leaded fuel. At the time I replaced the plugs, and until this weekend noticed nothing strange. I have not noticed any misfires yet.
One other detail is that most of the time I fill up with Chevron 91, but for both the autocross and this we