Thanks Ian, mid range is where I'm leaning to I suppose, the acceleration from 60 up.
Yes, I don't think its a perception thing, put shell 99 octane in and it does feel a bit more urgent than ordinary unleaded, but the Tesco just seems better. I read somewhere that Tesco just put more alcohol (Ethanol) in to raise the octane. In days gone by that would have made the mixture wrong since ethanol contains much more oxygen that petrol. Modern engines just add more fuel to compensate, so higher octane for more advance on the ignition, more oxygen and more fuel = Bigger bangs.
I did do a "learned parameters reset" when I switched to 99 Octane just to get it to learn the new fuel more quickly, i used multiecuscan to do that.
My Impreza turbo was the same, 99 Octane and an ECU reset and it definitely went better, probably because it could use more boost. The effect on that car was even greater.