Most A4/S4 cars are stolen by manually unlocking the drivers door with a screwdriver or other implement which is used to puncture the door skin and then to locate the Lock cylinder to lock mechanism arm, and then by manipulating this arm the door can be unlocked.

Procedure

1. Remove door panel from drivers side and Passenger side (pre 99.5)
2. Locate lock cylinder
3. Disconnect metal arm from lock cylinder
4. Remove white/yellow plastic cuff from lock cylinder (pull)
5. Follow lock arm down to door lock
6. Unscrew the metal arm from the black connector on the lock housing.

Once this arm is removed the door can no longer be manually unlocked. The key will still work in the door lock to unlock/lock the doors of the car.

What this achieves

The door is no longer manually unlocked by using the key in the door. Using the key in the door now tells the alarm system to activate the vacuum pump which then locks/unlocks the doors.

Unlocking the doors from the drivers door will now require 2 twists to the left. it used to require 1 to unlock the drivers door and 2 to unlock all doors.

This modification can also be done to the 99.5+ cars which only have a drivers door lock. 99 and earlier cars have both passenger side and driver's side keyholes. Both sides should be modified incase a passenger side break-in is attempted rather than the driver's side.

Email me back and I'll shoot pics of how to do this.