I don't have them, so I'm not your best source of info here, but from what I've heard they really don't do much of anything for you performance wise. Generally if it's cheap, than any HP gain you get from it will be to small to feel. There are exceptions, and I'm sure someone is going to tell you they are great but I'd say don't bother, put the money twards something more useful, like say an adjustable timing plate from ricky stator ($35 plus shipping) if you don't already have one.