first off, welcome to bimmerwerkz, glad your here to share your love for BMW;s.....
secondly did you do this brake job yourself? if so did you remember to resurface the rotors? and if you did , did you make sure that there was sufficient rotor left to run on? that could very well be the root to the unsteady braking patterns..
for the squeeling, im curious as to what pads you used or went with. and if you took the time to seat the pads properly... normally when you get new brakes its a good idea to take the car for a few good stops right away, its seats the pads properly ..
whats happening, for those who may be curious is , the brake pads all have a resin that is part of the pads, when the pads "glaze" the resin acts much like the resin on the bow of a violin.