Juan, GIAC has a map for a stock GT-3 and RS. Not tuned for aftermarket exhaust systems that I know of. Maps on stock engines should make about 12 hp and torque.
Just ask your GIAC dealer if they have a map specificly for the RS or tell them what flywheel you are running and the weight of it. Like I have said, we utilized REVO's which gave us a baseline RS map and we tuned it from there getting additional power out of headers. The increase was far more dramatic than maping a stock car. It's was like a different car, that different ! Tuning for a good exhaust system will be the most significant increase in engine performance you will make on the GT-3. I test drove my car on the standard map and it was just a little better. After we made further adjustments the motor came alive ! You could hear the difference, feel the difference and you find yourself shifting much faster cause it's reving up faster. I'm sorry I don't have dyno results. I know when a Porsche motor is working better.

 

The fitment for the front wheels of the GT3 and RS are the same. The rear offset for the RS is 17mm less than the GT3. The rears are not interchangeable.

 

Unless they have a map done for your exact engine package, exhaust, flywheel, etc.you will never be assured of the exact engine tune for best results. That's the beauty of REVO. A good local technician who can dial your car right in, that's the best case senario. As GIAC get's more cars in the dyno room, they will develope maps for various engine packages with headers and mufflers. There is good activity on the GT-3 so it will happen. I called Todd at EVO before I got my car looking for a map. Wasen't ready yet ! Steve