If I was tuned for 93 octane, do I need a retune if I use a 93 octane with 10% ethenol?

 

not really needed if you are tunned with some margin of error.
If you have tunned for bleeding edge, Yes, It will require retune. I have noticed the difference when my gas station started using 10%ethanol. Bit of ethanol will make AFR leaner bit... But not too much.