Your Porsche Cayenne TT(R) engine is controlled by very sophisticated Bosch(R) ME7xx Electronics, which carry out thousands of functions in the course of a short drive. Evolution Motorsports worked hand in hand with the engineers at GIAC to develop incredible computer upgrade programs. They have spent countless hours integrating numerous new ignition, fueling and boost calibrations into the stock programs. We are able to replicate a factory smooth power curve while increasing horsepower and torque throughout the RPM range.
Yes it can void the warranty if detected.
Costs from GIAC are about $2200 with a handheld flashloader (which switches the DME "chip" from performance back to stock prior to bringing in the car for repairs, then back to performance when you get the car back )
Another solution to make it more "undetectable" would be to purchase another DME from your dealer, keep the original, swap it out with the new one and modify the new one. If any major repairs are needed - engine/turbo repairs - then have the dealer replace the original prior to working on it.
A relationship with the dealer is needed, and they should do all mods for you so they see you are spending money with them. They can even send your car out for the tuning if they don't do it. But carry out the mods through them. This is the safest way to keep them in your corner with any repairs.
Contact EVO and they can give you authorized dealers in your area.
There are other tuning companies out there, but from everything that I have read of people's experience, EVo gets great reviews.
Other simple things can be done in addition or instead of the DME upgrade that will boodt your HP, and not void your warranty. High performance BMC air filters, or the new EVO V-flow air intake, and Fabspeed Cat Bypass pipes too.
I will be doing these upgrades at the end of April once the Evo intake system is released. So personally I can't tell you if it is worth it. But EVERYONE that does do it says..."yes, every penny."
Check out EVO's link here for this topic.
http://www.evoms.com/Cayenne%20TT%20main.htm#computer