So my 2006 WR450F was purchased used with the "pea shooter" removed. I have read a lot of the threads discussing opening up the exhaust and keeping the bike quiet. I had a few questions that I couldn't quite get to the bottom of: 1) Is the stock exhaust running without the pea shooter equivalent to the after market mufflers as far as power is concerned. That is to ask if I am ok with the noise level is there still power left to be gained by using a YZ or aftermarket muffler? 2) Would adding the Pro Billet in the above setup lessen power and decrease noise. Basically I'm trying to determine what is left to get out of the bike via the exhaust. Thanks guys.