I bet its rotors. Jack the front of the car up take your wheels off, look to see if there are hot spots on the rotors. Put the car in neutral spin the rotors if it feels like there is a area that's harder to turn it past most likely its warped. (ghetto run out test) I get a bad vibration when braking around 100+ mph but not during normal driving, I have cheap rotors maybe you do too. Good luck