This video shows just that and basically it comes down to being tuned to run 91 or above. Without changing your tune there is not that much performance difference but change your tune to match your fuel and yes there is a significant difference.
I don't know if the way that the spyder "adjusts" itself for fuel would take advantage of the fuel or detune the performance in order to maintain a status quo.
You would need to get one of the monster guys or some of other tuning specialist that frequent the site to explain it to us.
But I like his summary.
If you are going to run 87 be tuned
If you are going to run 93 be tuned
if you are going to run 93 in a 87 tune you will be ok with no significant performance difference.
If you are going to run 87 in a 93 tune you will probably blow the f up!... roflmao
https://youtu.be/Y6ndNhxlZB0