I put a set of road house pipes on my 08 900 and it increased my mpg by 6.5 mpg...asked my dealer about any changes I need to do and he said no, he said I might see a little diff. in throttle response but I did´nt, said if I did just remove pos. and neg. cables for 24 hrs. and the comp. would reset its self,,,but I am going to put a power comander on to stop back fire,,,ride safe