actually, the most power is made with the lowest octane, if your car doesn't need 93 octane but can run on 87 fine, use 87. lower octane gas have more potential energy stored, but higher octane resist detonation better. in your turbo hatch using 91 octane switching to 93 could give you more power if you retuned your ecu and raised the boost/ messed with the timing a bit.

 

well the timing has already been redone and the ecu reflashed, i just dont want to risk detonation with lower octane gas

 

As I mentioned before(see my posts above), I use 50%/50% water/methanol mixture and that workes great. Methanol is a form of alcohol, but never ever use rubbing alcohol as that will ruin your seals and mess up the pump quickly. I use aquamist products for my water/meth injection which is very pricy, but has a good reputation.

 

getting a good tune and running on 93 will be fine. It is all in the tune. If you go to a good tuner they will tune your car according to the fuel you are going to use, making the max power at the safest level.