as mentioned before, you can go up to e50 on stock injectors, but you will be limited to stockish boost. I suspect you could get away with a 3.4 if you had a few mods and you could run clean at 13:1afr.
Would be fine. You can mix it with 87 if you are on a stock pulley.what about like a 7 to 1 ratio of 93 and e85 to raise the octane rating mixing at the pump?