other than e85, Interesting to see you want to run 98. I'll be a loose cannon and say consistent 98 supplies can be just as tough to find in some regions as e85. I was struggling to get 95 yesterday for my f6. I'm going to say head porting, plus a valve spring upgrade. Lewis engines offers "affordable porting". I'm going with a formal flow tested port on my build.6 boost manifolds are nice.