The Audi TT, which stands for Tourist Trophy (a race in Europe), is a compact luxury coupe based on a heavily modified VW Golf platform. It is a perennial favourite in the European import tuner scene because it is easy to work on and relatively cheap for a German luxury car. A nice aesthetic feature of the TT is that the fuel flap is a separate chrome piece that can be repainted or even replaced by the car's owner.
Turn the Audi TT off and go to the rear passenger side where the fuel tank flap is located. Push in on the outer edge of the flap to unlatch it and pop it open.
Locate the three Phillips head screws that lie along the inside rim of the fuel flap collar equidistance from each other. Unscrew each screw and keep the screws somewhere safe for possible reuse. Slide a flathead screwdriver into the seam between the inside rim and car body. The collar is also cemented onto the body panel, but it can be separated with a light rocking back and forth.
Pull the collar with the fuel flap off the body panel slowly as it is still attached to the door sensor. The door sensor tells the Audi TT when the fuel flap is open and when it is closed. Unplug the door sensor from the fuel flap collar and drape it down on the side. If you are going to paint the Audi TT with the fuel flap off, tape over the hole to prevent paint from sealing the gas cap shut.
The flap serves to help keep in gas fumes and is regulated by emissions regulations.