I just installed a new "Muzzy" complete exhaust system with there quite core and spark arrestor screen. They told me at the time I ordered it that it would run at 94db. At the Sawmill enduro they tested it at 97db, 1 db over acceptable limits. I contacted Muzzy's and they told me that it tests fine in there tests. To appease me they are sending me some packing (Whoopie). So YZ owners I would recomend another brand of exhaust if you need to get below 97db.