vibration in front end

I am fighting a front end vibration problem in a 2005 325I.It is my boss's used car lot car he bought at the auction Tuesday to sell and it is driving me nuts.I checked the front end good and nothing wrong there.Balanced the front tires too,on the money.I even rotated them to the back even balanced the rear tires putting the rears to the front and vibration is still there.It is sold,to me and I like the car when it is fixed.Anything I missed?