From my experience, say if a car takes x amount of timing on 98RON - on E85 or similar water/meth that particular load point at y rpm will take 4~5 degrees more timing and make more power and torque.
But very hard to say in your situation without a dyno.
I usually start with a flat timing map then add timing till I start to see less power gains throughout the RPM range, then I determine where max torque is achieved and where it starts to heavily decay. This is where timing can be added (from where the torque decays) and then same thing, see if the motor will take timing at that point onwards.
Usually if 1x degree of extra timing makes less than 5kW of power it's pretty much a sign to stop adding timing.
Take whatever I say as only information, every motor, every fuel combination, every tuner etc.. is different. Also a good way to preserve motors is to run it richer at peak torque. The cars I tune (mostly for friends) run about 11.5 AFR at peak torque then lean up to about 12afr all the way to redline (that's E85 converted to Gasoline scaling).