I am currently running a ProCircuit header and silencer on my yz426. However, in the UK more and more tracks are doing noise testing and some only let on thumpers if they have an enduro or Q pipe. With this in mind I have just bought a full WR426 system from ebay. I might stick on the stock header and run the Arrow silencer and then if needed put on the wr silencer. Does anybody else run a YZF with a WR silencer. I realise it may take some power away. This isn't going to be a problem as the bike has more than I can handle. My main worry is how it is going to run. Any thoughts or experiences.