Custom programmed by RS-Tuning to optimize for 91 octane Cali gas. I actually shipped a very significant amount of 91 gas to them for this purpose. Long story, BUT if you have a 996TT X-50 (will not fly with non- X-50) this will transform your already very fast car. RS tells me, and I absolutely believe, that they achieved flywheel dyno #'s of 520hp and 540lbft torque on 1.0 bar max boost. No CEL trigger. To use on your car requires a Porsche tech with OBD interface ability. I have all the drill-downs needed to make this work for your car and a Bay Area dealer tech to work with. Will quickly refund any buyer who is not awestruck by results. $1900 email grecomfs@surgical.net if interested. thanks.