Guys, how can adult, good money earning people, believe that a 25 HP gain on a normally aspirated car can be achieved through a software upgrade only without compromising reliability and performance of the car?
Not to speak about other things like environmental issues.

To make it clear: chip tuning on normally aspirated cars is pretty much the dumbest thing anyone can do. And: if your vendor tells you that the tuning isn't detectable, IT IS DETECTABLE. Even if the dealer looks for it, he can easily find out. Not to speak about Porsche when you have a warranty issue with the engine. Guess what, they demand a printout from your motronic and guess even more: you can kiss your warranty good-bye.

The "trick" with chip tuning on normally aspirated engines is simple: usually such "tuning" comes with a sport airfilter or a modified airbox, sometimes with a sport exhaust. The louder sound (exhaust, air induction sound, etc.) already makes people believe that their car is faster than before. The software itself usually is programmed to provide more power in the upper rev band, sometimes even passing over the factory rev limiter. So you may get 20 HP more in the upper rev range, maybe even over the rev limiter but at the same time you'll loose power and especially torque in the mid and lower rev range.

There are so many possibilites using a different software, the general advise is: whatever you think, whatever the vendor tells you, don't do it. Nothing is for free in life, I always thought that at least people who can afford a 997 learned this lesson.

Regarding the X51 kit: ripoff? Well, maybe. Especially since it seems that Porsche developped this kit along with M97 engine development. But you don't get only reliable 26 HP more, you get a perfectly adapted integrated system.
And not to forget the fact, that a lot of 997 X51 engines are rumored to hit 400 HP.

But I don't want to sound like a teacher or a smarta... Do what you want with your money but what you're doing doesn't make much sense. Better sell your car and get a GT3. Or get a 997 Turbo, there are plenty possibilites to raise power by at least 40 HP without compromising reliability or the general setup of the engine. But even 911 Turbo drivers learned it the hard way that chip tuning is a possibility to increase power but although cheap, not the best one.

But of course you won't listen, right?!