What does X51 consist of?

I'm thinking about getting a new C4S and have been on the Porsche car configurator. Adding the "Tuning" for $17k (I presume this is the X51 package) along with a few other common options brings the car quickly around 105k plus. At that rate, I may as well get an '01 Turbo. How much HP, etc. does the x51 offer? also, the "sport exhaust" or whatever...is that sound only or is there some performance gain here specifically? thanks in advance.

Only like 20 hp for those dollars and yes the sport exhaust is sound only. The TT is a much better choice than the 996 X51 for the same money.

The X51 PowerKit raises the HP figure from 320 to 345 HP and beefs-up the torque curve. This is what Porsche says: " Realise the potential of Porsche engineering. The desire to improve, to approach perfection, is at the root of every significant achievement - not least in the field of sports car design. At Porsche Exclusive, we've applied that principle to the technical potential of our cars. Inside each Porsche is a high-performance engine based on technology developed for the track. As well as offering peerless acceleration and flexible response, Porsche engines are rightly renowned for their exceptional durability and distinctive sound. Now you can add your own personal touch to the legendary performance of your Porsche. On the 911 Carrera, we can increase both power and torque by adding a remapped engine management system, revised intake and exhaust manifolds, as well as modified cylinder heads and camshafts."

After seeing the HP plot, I do not think I need the X51 option. The HP of x51 engine is less than the HP of standar engine until 4750rpm. I usually do not drive that hard. Except, passing cars, training 0-60 skills, tracking, and so on.