In contrast to a part-specific general operating permit, a part-specific technical report does not always constitute the permission to carry out a structural modification. But: The part-specific technical report generally contains the point “Fields of application”. For example, it may say: “The modification described in the appendix to the vehicles listed therein may be carried out in compliance with the conditions and instructions specified therein.” In this case, the part-specific technical report contains direct permission to retrofit the wheel/tyre combinations listed in the appendix. Volkswagen also has the relevant part-specific technical report from the MOT authority for the approved wheel/tyre combinations specified in the CoC.
Most importantly, however, a part-specific technical report contains requirements concerning how the respective part is installed. Without an approved appendix, the MOT authority (or an equivalent testing facility) must check that the modification has been correctly performed in accordance with the technical report. A registration office can only enter the structural modification to the vehicle in Part I of the registration certificate, formerly known as the vehicle registration document, once it has been accepted.