Ok, i have the article in front of me - Wheels August 2007. Here are the facts. Temp was lower than I quoted above - 8 degrees.

There is nothing in the article about altitude impacting time Ben.

Times tested with VBOX.

Track: Tooradin Airport
Temp: 8 degrees
Driver: Maurie Piatt

CTR
Speed at indicated 100kph: 92
0-60kph: 3.7
0-80kph: 5.3
0-100kph: 7.8
0-120kph: 10.3
0-140kph: 14.0
0-160kph: -
0-400m: 15.5 @ 148kph

Mini Cooper S
Speed at indicated 100kph: 94

0-60kph: 3.5
0-80kph: 5.2
0-100kph: 7.4
0-120kph: 10.0
0-140kph: 13.7
0-160kph: 18.7
0-400m: 15.4 @ 148kph

Golf GTI
Speed at indicated 100kph: 94

0-60kph: 3.7
0-80kph: 5.1
0-100kph: 7.3
0-120kph: 9.6
0-140kph: 12.8
0-160kph: 16.6
0-400m: 15.2 @ 153kph