Research has said to use: CRF 250x can; FMF Q4; DB Dawg insert. I called a guy with an FMF (not sure which model), and he says he thinks it is as loud as stock. True or not. The bike will be street legal and used to do some sightseeing in national parks, then parked at a cabin for limited street use. . Quiet would be nice for the other tourists. Any opinions on these choices. I wonder if I could put a DB in a FMF. Side note: apparently I can get AZ street legal plates thru the mail. Don't know yet if I have to have AZ address and driver's license.