I just installed an hmf muffler on my '03 400, and the supplied 170 jet. my cat ran great until this. now when I throttle from half to full, it starts rattling out and sputtering. I tried a 138 jet it dont seem to cut out as bad, but it still does, my k@n kit says to lower the the clip on the metering rod. has anyone tryed this, does anyone feel my pain. some body please help me.

 

i was planning to get an hmf pipe for my 03 400 too. From what it sounds like, the 170 they gave you is too rich if its starting to sputter like that and not be as bad when u go down in jet size. I cant help you anymore than that, sorry im not too experienced with carb'd engines...