Youre welcome. And because I barely drive it in the winter, let alone race it. 89 is way cheaper so i run that. But I also tuned for it and I can always scan it. When summer comes around and I go cruising around and go the track then ill switch to 91. I would recommend porting the SC. Its easy and said to kill some KR. just make sure you gasket match it afterwards.Thanks for actually saying something useful in here. I'm still considering porting the SC, I might do it this spring. Why don't you always run 91?