well they do and they work.
its not about just maximising bhp/torque...higher octane fuel helps prevent onset of pre ignition known as pinking / detonation.
that will kill your engine if you run too much boost with crap fuel.
but of course if the map is done properly it will cater for this and not run much boost.
Personally i think its a waste of money remapping if ur stuck using 95 RON.
that silkolene one treats 2 tanks of fuel. so £7.50 per tank. and you think thats expensive?
What till ur engine go bang then. also....what's the price difference between 95 RON and 99 RON fuel? I reckon 10p diff per litre...so on 1 tank that's £5-£6.
But hey its ur car so you do what u think is right.