Not everything is about power gains. Responsiveness gives you the illusion of power. The stock catalytic system has a pee hole for gasses to pass through. A freer system will alleviate all that unnecessary back pressure she has and make that 22 HP feel like 22HP has not 12 HP. Of course most of that responsiveness comes from the change in header diameter. All at the cost of your hearing and sanity! When I felt I needed to repack my Yoshimura I went to my local moto shop and brought up the loudness. He gave me a roll of packing (mat type stuff.. not the shredded kind) That was in essentially an unmarked bag. It made a noticeable difference which I was happy cause I still wanted to use my spark arrestor and not the “quiet” insert that it came with. Repacking is a pain.. rivets are worse.. but it worked. I’ll see if I can come up with some sort of manufacturer from the guy.