I'd add 4-5 gllons of E-85 and switch to map 5. As long as you don't go over 45% ethanol you'll be fine. Over 45% and you'll start running too lean which is no fun because of check engine lights and misfires.
If you don't want to run E-85, just stick with your 93 and switch to map 2 or 5 because you'll notice a huge torque/power improvement. Your IS can handle map 2 or 5 with no problem.