need help

I am basically new here and a first time Mustang GT owner. 2004 4.6L.
The mfg said 87 octane would be fine. But I already added premium 93 oct should I just go back to 87oct, I'd just thought that running higher octane would make for better performance...am I wrong?

Also I drove 115 miles (last time I do that(Trying to keep mileage low)) to NY from Pa and it only used up a 1/4 of my tank that's great!!!

p.s. What is IMHO, Jeff Chambers? Thanks again