I am putting an exhaust on my sons xr100 and need to know what jetting I should use. I already have a UNI pod filter and airbox is gone. I pulled the end cap off the stock exhaust and want to know if I should rejet. Is uncorking the end cap enough on these bikes, would a new exhaust really do much more over opening up the stock exhaust? thanks. Jetting now is stock and it seems to run great.