I have a 2009 klx250sf and i was to install a big gun evo r slip on. The part is supposed to fit 1994-2010 models. ( part number 09-4312) however; it just will not fit my bike....the inlet on the big gun is the exact same size as the stock exhaust gasket, and the big gun is much shorter than the stock exahust. I had to remove my exhaust gasket to make the big gun fit diameter wise, and when mounted properly, only about a half inch is seated in my header pipe. now it cannot seal properly due to my header having flared ends. does anyone know if the "slip on" requires the big gun header? or did i just get a defective part?