Re: Can someone summarize the mechanical similarities ....
As far as I know, the Cayenne and the Touareg have the same air suspension system. However the Cayenne has a more sporty setup.
Here's a little description of the Cayenne's air suspension:
Active damper control
Porsche offers pneumatic suspension in combination with Porsche Active Suspension Management (PASM), a brand-new variable damping system. Operated electronically, PASM adjusts damper forces infinitely as a function of surface conditions and the driver's style of motoring. A typical example of PASM intervention is when driving very dynamically with powerful application of the gas and/or brake pedal or when driving on particularly rough terrain, where PASM serves to steady any sway and dive motion of the body. This function is ensured by five accelerometers monitoring body movement. As soon as the motion of the Cayenne's body exceeds a certain limit depending on specific driving conditions, PASM will intervene, stabilising the vehicle by acting on the individual dampers.
PASM also gives the Cayenne driver the opportunity to choose his very own, personal damper setting while driving - with a choice of Comfort, Normal and Sports positions. Consistently operating in the background, PASM always maintains its active control function, comparing the driver's style of motoring with the program currently in use. Whenever the driver has chosen a particularly comfortable damper setting but is driving in a more sporting and dynamic style, the system automatically switches over to the sports mode and makes the dampers firmer.
I hope it helps to clarify things a little bit.