My Suzi has only 65hp left…

Good morning, was the penultimate Sunday on a dynamometer. Then came out what I had feared for a long time. And it doesn’t pull out as well as before. In terms of numbers this means: from 8000U/min the power drops and more than 53 hp on the rear wheel and (probably reached/estimated) 65hp on the engine. What do you think I should do now? Air Filter Candles Set Valves Synchronize Carburettors Let’s go from here I make the above things And after that it doesn’t get really better? is then even what broken or can this also be due to the age of my Suzi? (BJ 89) Greeting Tobi