35,000 miles on these originals. tuned since 1,200 miles. they all look good to me, i was wondering what the rust color on the porcelain is just above the metal hex part. are these heat marks? i changed these because im starting to get a multiple misfires on part throttle acceleration always after coming out of pe like a highway pass 70-90mph mid boost like 12-14 psi (running richer than 14:1) but before dfco is enabled on decelaration. gonna do a log tonight to see if misfires are gone. car runs great full throttle. this only happens in 4th and 5th gear on the highway part throttle. if i let dfco enable before giving it part throttle it accelerates fine. seams to only happen if the remaining cylinder charge is richer than 14.7