Pade mi na pamet, ovo su najnoviji, Euro5+ modeli. Moguće da su ih još uštrojili, tj. katalizovali, remapirali i šta sve ne, pa da i to ima efekat.
U stvari, ima sigurno veze. Euro5+ podrazumeva i propisanu jačinu emisije zvuka (!?) na manjim brzinama:
https://www.kamaxgroup.com/news/motorcycle-emissions-standards-understanding-euro-5-and-euro-5
Noise Emissions: Although Euro 5 focuses on pollutant emissions, Euro 5+ will tighten noise emission limits as well, aiming to reduce noise pollution. Motorcycles must now stay within 80 dB at 50 km/h (depending on the model), ensuring that they not only emit fewer pollutants but also contribute less to noise pollution
E sad, to što zvuk ima manje dB, ne znači da je i prijatniji za slušanje.