Hi, my uncle asked me to do some research for him on silencers for his 2004 Kawasaki KLX 300, because the stock one is a little less than pleasing. I found the FMF Power Core 4 for that bike, and also the Pro Circuit T4, both around the same price range. He is mostly a woods rider, but wants more of a power gain from his bike. He also wants to spend less than $400. Are those good silencers, or should I be looking for something different, Thanks.