without resetting the ecu you shouldnt ever see a gain neway
Resetting the only makes the change quicker. The ecu will foward ignition timing to suit the fuel whever or not you reset the ecu. Take 3 tanks to get it running properly on high octane.
Personaly i found tescos to cause my glanza to be a bit stuttery under accelaration. Switched to v-power and it sorted itself out.
Tescos 99 is not 5% methanol it is 5% bio-fuel different thing entirely.
However as you all have probably read all fuel is now atleast 2.5%bio-fuel now.