OK I'll stick my neck out again and risk being shot down in flames :D
Back in the old days lead was added to petrol as an "anti-knock" and the amount of lead added increased the Octane rating of the fuel. The higher the Octane rating the slower and more controlled is the burn of the fuel, "burn not bang". This allowed higher compression ratios and more advance of the ignition without inducing "pinking" (pre-ingition) and over heating, hence more power. Obvoiusly lead has now gone and petrol companies are using other additives to increase the Octane rating of the fuel.
However the compression ratio of the engine is fixed and the ECU is programmed for SUL, so using Optimax will not give more power but it will reduce your bank balance. Having said all that if you have a blower and the ECU has been re-mapped it probably will be better.