I am unsure of being different. I have just bought a pair of wishbones for my mk2 ST and have a larger balljoint (21mm over 19mm if I remember) but this is also fitted to the cmax and diesel focus's, so nothing special. The Mk1 ST will have differening damping and springs to standard and a stiffer ARB, but the wishbones are probably quite generic across the range. I am not sure what you mean by it 'popped out' the only thing I can see doing that is the strut to the upright, which you cant remove without taking the bolts out and you dont want that to happen !!