Is there a performance boost? Is it going to screw up my pistons?

Its a bone stock 07 STI.

 

The only way higher octane will help you is if you are tuned for it.

 

what kind of a tune and will it screw up my pistons?

 

A 100 octane tune. No. It'll actually rob power if you aren't tuned for it.

 

Your engine will make more power and torque with 100 octane fuel and a professional tune. The downside is you must always use 100 octane fuel with that specific tune. You can use lesser grades of fuel if you use a map-switching device such as the Cobb AccessPORT, but performance will be correspondingly less.

Do NOT try to use a 100-octane tune with typical pump premium (91 or 92 octane). Your engine may suffer severe damage from overadvanced ignition timing and higher turbo boost settings.

 

is it leaded?

if it is dont use it youll screw everything up



yes it will help your stock ECU will start to add timing and youll have more getty up you can feel

if you get a tune for 100 oct you will really notice it by a big difference

 

if you have oil in your intercooler than yes it will help since oil lowers your octane rating.