SoI have a Cobb access port and I had at the 93 stage one tun on it and then went to get gas from a top tier gas station and even before I left the gas pump I switched it to 87 octane tune from the Cobb and right away it went from -1.00 to -.50.
Your OAR runs from -1.00 to +1.00. You want to be at -1.00, which means your fuel is good and you aren't getting much knock. +1.00 would mean you had crap fuel and lots of knock. So it sounds like you had 93 octane in it when you switched to an 87 tune...which would cause the OAR to adjust in the proper direction...so assuming I understood you correctly, there's no issue and nothing to see here.