in about 4 years of installing m5 bushings i've yet to have a set crap out and come back to my shop, i have 46k miles on my set and short of track driving i am about as hard as you could be on them on the street, the closest i get to a **** up is on a road trip after i put a couple hundred miles on it or so without using the brakes they get pretty cool and i get a wobble or two when i finally use them and then it's gone, the main things i go after when squashing the shimmy is of corse replace any loose/worn/sloppy components first, then m5 bushings, new brake rotors (if it shimmeys under braking) strut inserts, things to pay attention to are, the idler arm, if you can move it up/down it needs a new bushing, the center link aka center tierod, if you can twist it or get any other play in the joints it's toast, loose steering box can screw with it a little too, sometimes you can adjust it but i find usually the later boxes the wear is in the bottom of the box and it's screwed, odditys i've come across, loose pittman arm and bad rag joint on the steering shaft. this may or may not be useful to you in your quest so good luck