You can run 87 on the level 3
BUT you have to lower the timing. I think when I was playing with it, I dropped it 2.5 to 3 on the programmer. I dont think it made much of a difference though.
I also tried it with the canned 93 so Im not sure how a custom tune will respond (probably same). Easy way to know how much to adjust, change timing .5 for every octane difference.