E85 is NEVER necessary. There is no way to tell what amount of boost will cause your car to detonate. If you get knock, pull boost and/or timing. You cant say “I’m going to run 10psi on 93 octane” because you don’t know what the motor will handle. Put 93 in the tank, start at nothing and work your way up until it knocks, then back it down to a safe level where you will not detonate regardless of altitude and/or weather conditions.
10psi on 2 different turbos is totally different. Larger turbos flow more air than smaller turbos. For example, I have a little 16g on my car at 22psi. If I ran a 35R on my car at 22psi, my head would take off like a rocketship right through my hood. LOL