[onewhippedpuppy]

A couple other things worth noting regarding the Cayenne:

Driveshaft failure = center bearing failure, which isn't uncommon on two piece driveshafts. There is an improved OEM and aftermarket fix available. It also gives a lot of warning before failure, so it's not catastrophic (typically).

The Cayenne air suspension isn't terrible but like all air suspensions, eventually will need TLC. Arnott Industries makes cheaper but high quality aftermarket replacement parts that will save you a ton over OEM. The other option is to simply not buy the air suspension, it was optional on the S. Though on my GTS it was quite good.

For the Porsche you can get Durametric for about $300 that gives you 90% of the dealer computer capability. I'm not sure if a similar system exists for BMW DIY work.