I think you will find it really depends on the state of tunning
If it is highly modified then you will need higher octain to get the benefits
I used to run an R34gtr could only use 98 or higher if I wanted to drive hard
If I used 95 it was fine till I tryed to push it
Then the ECU would retard the power and the car would not be able to drive hard
It was modified
With new ecu,cams,exhaust,induction,
Pushing just over 400 bhp