From the looks of the info on this site I am pretty sure that somebody can help me with this question. I am looking for a spark arrester for my recently purchased 98 yz400f. It came with both the stock muffler and an FMF muffler. Does anyone make a bolt on unit to avoid having to spend another $300 on the whole tail section? I do a fair amount of woods riding in ElDorado County, California so it is important to have something with the USFS approved stamp so when I come across Mr. Greenjeans my scooter is legal. Much appreciate any help from the vast banks of knowledge out there since most of my nearby dealers seem to be upset that a drawer in their register is lite, around $300. One more thing. Does anyone have any tricks to get that beasty growl down to a 101db level? Some of our OHV Parks are requiring this now.