Yes, higher octane fuel can handle more timing but still how hot the cylinder gets and what type of flow the engine have. higher RPM there is more gasses to exit off the exhaust so more heat, requires less timing. timing is added where the engine requires it to run smooth and with power, too much timing can cause the top of the cylinder to heat up and cause NOX .that's where the metal dioxide. the damage will be to the pistons and valves. you can add timing tell there is what they call knocks and back off few degree from there. you can use a knock sensor or temp sensor and in my case a Nox measurement in ppm. if you don't have any of those as I said before, timing can be added up to 5-6000 RPM as manufacturers retard those areas to pass emission regulation. adding Timing at the top end of RPM without any tools is something you shouldn't do. if you really want the power at the top end you do need a dyno and an experienced tuner. in your case with a cat, you should pay attention what air-fuel ratio you get after the cat . most cats require 14.7:1 ratio in order to work correctly and last long, too rich of a mixture can plug up the cat. If you have a high flow Cat then the richer mixture is ok with it but you need to check with the manufacturer to find out how much and what flow you getting from the exhaust before you start adding timing and running the mixture richer than manufacture.
