They don't change blends here in Colorado year round. There are two chains that carry E85, one is 70% year round and there are tons of stations around town and very close to my home. The other has consistent 87% year round but its pretty far and not as plentiful. I've been thinking about just changing the stoich setting in my tune to run 70%, but I am worried I will have to pull some timing to compensate for the lower octane. Are their any real octane or performance differences between 70% and 85% blends?