Originally Posted by STi_Guy04
...what do you all mean by the number when your talking about the mahle pistions? ...
Unabomber has a pretty good [and short] discussion of this in the Piston FAQ. As for specific "high power" piston recommendations, there was a thread in here recently that likewise talked about this. I'm using custom JE's, but others have had great results with CP and Wiesco too - irrespective of piston choice, the bottom line is there is no subsitute for proper fit and engine assembly work.
As for your injection question, light water injection only is fine without a retune, but shooting in extra fuel (ie, water/meth mix) without a retune is not the best idea. I've heard several tuners (Azscoobie among them) mention problems including "rich detonation" here, but frankly that is not something I'm qualified to talk about. Perhaps Mick or other tuners can chime in...