Sorry for reviving an old thread.
Biggynuts01 has a good point about the problem coming and going after making turns.
I've been plagued by this problem the whole time I've had my second e90. I have it with both the stock wheels and my RG63s. It is related to how the right and left side tires interact. I just finished 500 miles on the PA turnpike after my second thorough RF balance. At 75 mph the car can be smooth as silk. As the road turns I can feel the vibration come back and it stays until the road either turns more in that direction or the road turns back towards the direction I was originally traveling in. This is driving me nuts.
Dinan compliment of stuff plus PF rotors and RG63s. Enough for now.
Why, yes. I am an abrasive bastard.