Depending on the sputter sounds it could be rich or lean. hows the acceleration up until it dies is it good or is it bad. Im thinking that it could be rich but im also leaning towards lean. Just try richening the HSN up a bit a if it helps keep on doing it till it gets to the performance you like. Or if it just makes it worse try leaning it out then. It is aslways better to be rich then lean so Thats why I said to richen it up first.