Just got a stainless RS4 system for my 2012 YZ450. In Australia they only come with the spark arrestor insert. And the other inserts, if you can figure out which one to get, are hard to come by. The shop that sold it to me told me to just pull it out and run no insert, i'm yet to hit the track with it but it's clearly louder.
I don't have any noise restrictions to worry about, just my ears and those riding around me.
So my question is: What insert do you guys without noise restriction run ?