After the very amusing 488 Pista discussion, I have another delicious topic for you. The Picture above shows the notebook from Roland Kussmaul (taskmaster 993 GT2). This is his entry for the 993 GT2 run from 26.07.00 on the Nordschleife with Walter Röhrl.
"26.07.00 Fg 416 Nbrg trocken Walter R.
Benzin 102 --> Steuergerät +6°
Luftdruck 2,0/2,2
Pirelli 225/285 auf 4 mm abgeschliffen
Stabi 5/3"
«Benzin 102 --> Steuergerät +6°» means they used 102 octane and changed the ignition timing to +6° advance ignition. This result in more top end power compared to the stock cars.
«Pirelli 225/285 auf 4 mm abgeschliffen» means they removed half the tread with tools before mounting the tires. This improves slip angle and tread rigidity.
To me – this looks like cheating ;)
Source: Auto Motor und Sport