I could be wrong but I don't believe unused octane "loads up" Your thinking of thermoquad problems not modern fuel injection. You were able to buy the Scat Pac, surely you can drop that extra $2 a tank for premium!

We use the recommended 89 or 91 in the Wife's 18 RT Durango with the 5.7. If you roll into the throttle I feel like it has a flat spot where it is pulling timing for some reason or another. I need to put a catch can on it just to rule oil in the intake out.