PLEASE READ BEFORE POSTING: This is not one of the many extremely over-posted threads about what is the best pipe for a 06-09 yz450f. This post is for riders with quiet exhaust systems to provide input and suggestions, or anything to do with a quiet exhaust system. I am looking for a slip-on muffler or complete system for a 2006-2009 yz450f. It needs to have a U.S.F.S approved spark arrestor( including the stamp on the muffler can saying that the muffler is USFS approved), as well as EASILY and continuously pass the 96db limit. I am not looking for a pipe that I have to re-pack every ten hours to pass a sound test. I've looked at some of the exhaust systems available, and already eliminated a few. I am looking for a durable and reliable exhaust as well. Pro-circuit: Too expensive for what I'm looking for. MRD: many recommendations from other riders in different forums, but it does not have the U.S.F.S approved stamp. Vance & Hines ( White bro's): I have a friend who bought an exhaust system from them. The spark arrestor insert constantly rattled loose, even with a weld holding the insert in! I am wondering how exhaust systems, such as Dr.D, FMF 4.1, and others, work when they have the 96db( same as "94db" to the FIM) insert? How close are they to failing? How do they perform? Does the muffler have to re-packed constantly to pass sound tests? I know the FMF Q4, or even a take-off WR muffler are the easy and very quiet choices, but I want to explore all my options:smirk:.