I don´t know if the baffle in the ´slip on´ stock muffler is removable..Your best bet is to get rid of the stock exhaust all together. Lots of really good options for the 04/05 XL have come out just recently. I have ´jug huggers´ from BUB exhaust, a stepped header with a small baffle and BEAUTIFUL chrome. the header design with a rejet is good for about 10+ HP boost http://www.bubent.com/