Motorcycle letter and bill bzg. Performance data not identical – what to do?

Hello! I have to sell a motorcycle (CX500) and have now, after I have selected the letter out something strange found: In the letter the machine is indicated only with 20 KW, in the appearance also with 20 KW additionally but with power increase to 37KW. The old letter was drawn in when I had registered the machine for the first time. The CX is now 37KW insured and in this constellation with the corresponding components (gassers and manifolds each 37KW) also new TÜ V. The appearance and the letter were handed out as they were from the office but now I am worried that the note for increased performance in the letter is missing. What should I do now? Many greetings