You described my exprerience in my MB to a 'T' Gary. It was more noticable than I find on the Cayenne, I always knew what it was doing (or not) and could always fix it. If I started driving aggresively it would respond and continue in that "mode" for the journey (mostly home across country from the office at about 1am) and that thing would fly.

The next morning it would start off the same but after a short while during the regular commute it would revert to sedate/smooth mode.

On the MB it coincided with hitting the "emergency" power button at the bottom of the gas pedal travel, that way it "knew" what you wanted to do it did not have to "guess" or calculate based on behavior.

As I said in another post, they should modify the PSM button to also switch to a sport mode, that would shut everyone up (coffee spillers and racers).