According to an HMF rep who has contacted me via email, The Hunter Q-core reduces db levels to 91db and keeps 95% of the power gain ($35), while the regular quiet core reduces sound levels to 95db and keeps 80% of the power gain. Without the q-core (98db's). It is not recommended in anyway by HMF that the air box lid be removed. Spark arrestors are made with USFS specs, approval is in the works. Jetting is 170 for slip-ons. Different technology requires different mods. The hunter core offers, "all the power without all the noise". HMF claims they have over two years in development of the Hunter core. According to an HMF rep, These specs are not claims, they are facts that are proven through research and development.