I don't know how you drive but it sounds like maybe you have some suspension parts worn out, could be tires need balancing. Have you checked/ replaced recently your control arms, CAB's, tie rods, etc. You said you recently replaced your breaks, pads, did you do it yourself or at a shop? If you do a lot of things at home, you shouldn't have a problem checking your front suspension if worn out, just an idea.
there are plenty of threads here about vibration in high speed, i suggest you do a search in the forum, just type vibration and whole bunch of threads will come out, just dig through. Cheers
sample below:
http://www.unitedbimmer.com/forums/m...45-65-mph.html