I can let you know how the mods i have done to a 07 M1 worked after saturdays dyno session.:d For starters a boondocker, jaws twins,v-force three's and the wrest well i'll let you know. However i was told by a rweliable source a few minutes ago a SLP single on a completely stock engine makes 25hp more than the stock pipe and you loose 14lbs.