There no such a thing as a "Tiptronic S" on the 958 Cayenne. It's called Tiptronic, and that was the only automatic gearbox option on that car. I own the exact same car, with a Malone Stage II ecu upgrade and I did 143MPH gps which is 230kph.
The best 6 cylinder diesel engine is from Renault, the 3.0 V6 dCi with 240 hp, found in Latitude and Laguna coupe. Mercedes also has very good 6 cylinder diesel engines. A 320 CDI is a fantastic engine throughout.
