Steering wheel vibration

[Awdrex]

So I've been having the symptoms of a wheel balance issue for over a year now and it's getting annoying. It can't be wheels or tires cause I've had several sets of tires and two sets of wheels on the car all which have been balance and checked and the vibration persists.

What else could it be?
It only happens at highway speeds.

Thanks for the input in advance

 

[Awdrex]

I'm thinking tie rod ends....

 

[Undecisive]

Have you checked your wheel bearings? Worn out wheel bearings are known to cause that issue.

 

[STimedic]

Check your wheel bearings, when's the last time your ball joints and tie rod ends were replaced? Alignment done? Or if you have an 02-04 WRX and 04 STi, it could well be the steering rack bushings, but usually that causes wandering around while driving....

There's lots of stuff to check, check it to rule out what is causing it.